data_transforms.py

# Copyright 2021 AlQuraishi Laboratory
# Copyright 2021 DeepMind Technologies Limited
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import itertools
from functools import reduce, wraps
from operator import add

import numpy as np
import torch

from openfold.config import NUM_RES, NUM_EXTRA_SEQ, NUM_TEMPLATES, NUM_MSA_SEQ
from openfold.np import residue_constants as rc
from openfold.utils.rigid_utils import Rotation, Rigid
from openfold.utils.tensor_utils import (
    tree_map,
    tensor_tree_map,
    batched_gather,
)


MSA_FEATURE_NAMES = [
    "msa",
    "deletion_matrix",
    "msa_mask",
    "msa_row_mask",
    "bert_mask",
    "true_msa",
]


def cast_to_64bit_ints(protein):
    # We keep all ints as int64
    for k, v in protein.items():
        if v.dtype == torch.int32:
            protein[k] = v.type(torch.int64)

    return protein


def make_one_hot(x, num_classes):
    x_one_hot = torch.zeros(*x.shape, num_classes, device=x.device)
    x_one_hot.scatter_(-1, x.unsqueeze(-1), 1)
    return x_one_hot


def make_seq_mask(protein):
    protein["seq_mask"] = torch.ones(
        protein["aatype"].shape, dtype=torch.float32
    )
    return protein


def make_template_mask(protein):
    protein["template_mask"] = torch.ones(
        protein["template_aatype"].shape[0], dtype=torch.float32
    )
    return protein


def curry1(f):
    """Supply all arguments but the first."""
    @wraps(f)
    def fc(*args, **kwargs):
        return lambda x: f(x, *args, **kwargs)

    return fc


def make_all_atom_aatype(protein):
    protein["all_atom_aatype"] = protein["aatype"]
    return protein


def fix_templates_aatype(protein):
    # Map one-hot to indices
    num_templates = protein["template_aatype"].shape[0]
    if(num_templates > 0):
        protein["template_aatype"] = torch.argmax(
            protein["template_aatype"], dim=-1
        )
        # Map hhsearch-aatype to our aatype.
        new_order_list = rc.MAP_HHBLITS_AATYPE_TO_OUR_AATYPE
        new_order = torch.tensor(
            new_order_list, dtype=torch.int64, device=protein["aatype"].device,
        ).expand(num_templates, -1)
        protein["template_aatype"] = torch.gather(
            new_order, 1, index=protein["template_aatype"]
        )

    return protein


def correct_msa_restypes(protein):
    """Correct MSA restype to have the same order as rc."""
    new_order_list = rc.MAP_HHBLITS_AATYPE_TO_OUR_AATYPE
    new_order = torch.tensor(
        [new_order_list] * protein["msa"].shape[1], 
        device=protein["msa"].device,
    ).transpose(0, 1)
    protein["msa"] = torch.gather(new_order, 0, protein["msa"])

    perm_matrix = np.zeros((22, 22), dtype=np.float32)
    perm_matrix[range(len(new_order_list)), new_order_list] = 1.0

    for k in protein:
        if "profile" in k:
            num_dim = protein[k].shape.as_list()[-1]
            assert num_dim in [
                20,
                21,
                22,
            ], "num_dim for %s out of expected range: %s" % (k, num_dim)
            protein[k] = torch.dot(protein[k], perm_matrix[:num_dim, :num_dim])
    
    return protein


def squeeze_features(protein):
    """Remove singleton and repeated dimensions in protein features."""
    protein["aatype"] = torch.argmax(protein["aatype"], dim=-1)
    for k in [
        "domain_name",
        "msa",
        "num_alignments",
        "seq_length",
        "sequence",
        "superfamily",
        "deletion_matrix",
        "resolution",
        "between_segment_residues",
        "residue_index",
        "template_all_atom_mask",
    ]:
        if k in protein:
            final_dim = protein[k].shape[-1]
            if isinstance(final_dim, int) and final_dim == 1:
                if torch.is_tensor(protein[k]):
                    protein[k] = torch.squeeze(protein[k], dim=-1)
                else:
                    protein[k] = np.squeeze(protein[k], axis=-1)

    for k in ["seq_length", "num_alignments"]:
        if k in protein:
            protein[k] = protein[k][0]

    return protein


@curry1
def randomly_replace_msa_with_unknown(protein, replace_proportion):
    """Replace a portion of the MSA with 'X'."""
    msa_mask = torch.rand(protein["msa"].shape) < replace_proportion
    x_idx = 20
    gap_idx = 21
    msa_mask = torch.logical_and(msa_mask, protein["msa"] != gap_idx)
    protein["msa"] = torch.where(
        msa_mask,
        torch.ones_like(protein["msa"]) * x_idx,
        protein["msa"]
    )
    aatype_mask = torch.rand(protein["aatype"].shape) < replace_proportion

    protein["aatype"] = torch.where(
        aatype_mask,
        torch.ones_like(protein["aatype"]) * x_idx,
        protein["aatype"],
    )
    return protein


@curry1
def sample_msa(protein, max_seq, keep_extra, seed=None):
    """Sample MSA randomly, remaining sequences are stored are stored as `extra_*`.""" 
    num_seq = protein["msa"].shape[0]
    g = torch.Generator(device=protein["msa"].device)
    if seed is not None:
        g.manual_seed(seed)
    shuffled = torch.randperm(num_seq - 1, generator=g) + 1
    index_order = torch.cat(
        (torch.tensor([0], device=shuffled.device), shuffled), 
        dim=0
    )
    num_sel = min(max_seq, num_seq)
    sel_seq, not_sel_seq = torch.split(
        index_order, [num_sel, num_seq - num_sel]
    )

    for k in MSA_FEATURE_NAMES:
        if k in protein:
            if keep_extra:
                protein["extra_" + k] = torch.index_select(
                    protein[k], 0, not_sel_seq
                )
            protein[k] = torch.index_select(protein[k], 0, sel_seq)

    return protein


@curry1
def add_distillation_flag(protein, distillation):
    protein['is_distillation'] = distillation
    return protein

@curry1
def sample_msa_distillation(protein, max_seq):
    if(protein["is_distillation"] == 1):
        protein = sample_msa(max_seq, keep_extra=False)(protein)
    return protein


@curry1
def crop_extra_msa(protein, max_extra_msa):
    num_seq = protein["extra_msa"].shape[0]
    num_sel = min(max_extra_msa, num_seq)
    select_indices = torch.randperm(num_seq)[:num_sel]
    for k in MSA_FEATURE_NAMES:
        if "extra_" + k in protein:
            protein["extra_" + k] = torch.index_select(
                protein["extra_" + k], 0, select_indices
            )
    
    return protein


def delete_extra_msa(protein):
    for k in MSA_FEATURE_NAMES:
        if "extra_" + k in protein:
            del protein["extra_" + k]
    return protein


# Not used in inference
@curry1
def block_delete_msa(protein, config):
    num_seq = protein["msa"].shape[0]
    block_num_seq = torch.floor(
        torch.tensor(num_seq, dtype=torch.float32, device=protein["msa"].device)
        * config.msa_fraction_per_block
    ).to(torch.int32)

    if config.randomize_num_blocks:
        nb = torch.distributions.uniform.Uniform(
            0, config.num_blocks + 1
        ).sample()
    else:
        nb = config.num_blocks

    del_block_starts = torch.distributions.Uniform(0, num_seq).sample(nb)
    del_blocks = del_block_starts[:, None] + torch.range(block_num_seq)
    del_blocks = torch.clip(del_blocks, 0, num_seq - 1)
    del_indices = torch.unique(torch.sort(torch.reshape(del_blocks, [-1])))[0]

    # Make sure we keep the original sequence
    combined = torch.cat((torch.range(1, num_seq)[None], del_indices[None]))
    uniques, counts = combined.unique(return_counts=True)
    difference = uniques[counts == 1]
    intersection = uniques[counts > 1]
    keep_indices = torch.squeeze(difference, 0)

    for k in MSA_FEATURE_NAMES:
        if k in protein:
            protein[k] = torch.gather(protein[k], keep_indices)

    return protein


@curry1
def nearest_neighbor_clusters(protein, gap_agreement_weight=0.0):
    weights = torch.cat(
        [
            torch.ones(21, device=protein["msa"].device), 
            gap_agreement_weight * torch.ones(1, device=protein["msa"].device),
            torch.zeros(1, device=protein["msa"].device)
        ],
        0,
    )

    # Make agreement score as weighted Hamming distance
    msa_one_hot = make_one_hot(protein["msa"], 23)
    sample_one_hot = protein["msa_mask"][:, :, None] * msa_one_hot
    extra_msa_one_hot = make_one_hot(protein["extra_msa"], 23)
    extra_one_hot = protein["extra_msa_mask"][:, :, None] * extra_msa_one_hot

    num_seq, num_res, _ = sample_one_hot.shape
    extra_num_seq, _, _ = extra_one_hot.shape

    # Compute tf.einsum('mrc,nrc,c->mn', sample_one_hot, extra_one_hot, weights)
    # in an optimized fashion to avoid possible memory or computation blowup.
    agreement = torch.matmul(
        torch.reshape(extra_one_hot, [extra_num_seq, num_res * 23]),
        torch.reshape(
            sample_one_hot * weights, [num_seq, num_res * 23]
        ).transpose(0, 1),
    )

    # Assign each sequence in the extra sequences to the closest MSA sample
    protein["extra_cluster_assignment"] = torch.argmax(agreement, dim=1).to(
        torch.int64
    )
    
    return protein


def unsorted_segment_sum(data, segment_ids, num_segments):
    """
    Computes the sum along segments of a tensor. Similar to 
    tf.unsorted_segment_sum, but only supports 1-D indices.

    :param data: A tensor whose segments are to be summed.
    :param segment_ids: The 1-D segment indices tensor.
    :param num_segments: The number of segments.
    :return: A tensor of same data type as the data argument.
    """
    assert (
        len(segment_ids.shape) == 1 and
        segment_ids.shape[0] == data.shape[0]
    )
    segment_ids = segment_ids.view(
        segment_ids.shape[0], *((1,) * len(data.shape[1:]))
    )
    segment_ids = segment_ids.expand(data.shape)
    shape = [num_segments] + list(data.shape[1:])
    tensor = (
        torch.zeros(*shape, device=segment_ids.device)
        .scatter_add_(0, segment_ids, data.float())
    )
    tensor = tensor.type(data.dtype)
    return tensor


@curry1
def summarize_clusters(protein):
    """Produce profile and deletion_matrix_mean within each cluster."""
    num_seq = protein["msa"].shape[0]

    def csum(x):
        return unsorted_segment_sum(
            x, protein["extra_cluster_assignment"], num_seq
        )

    mask = protein["extra_msa_mask"]
    mask_counts = 1e-6 + protein["msa_mask"] + csum(mask)  # Include center

    msa_sum = csum(mask[:, :, None] * make_one_hot(protein["extra_msa"], 23))
    msa_sum += make_one_hot(protein["msa"], 23)  # Original sequence
    protein["cluster_profile"] = msa_sum / mask_counts[:, :, None]
    del msa_sum

    del_sum = csum(mask * protein["extra_deletion_matrix"])
    del_sum += protein["deletion_matrix"]  # Original sequence
    protein["cluster_deletion_mean"] = del_sum / mask_counts
    del del_sum
    
    return protein


def make_msa_mask(protein):
    """Mask features are all ones, but will later be zero-padded."""
    protein["msa_mask"] = torch.ones(protein["msa"].shape, dtype=torch.float32)
    protein["msa_row_mask"] = torch.ones(
        (protein["msa"].shape[0]), dtype=torch.float32
    )
    return protein


def pseudo_beta_fn(aatype, all_atom_positions, all_atom_mask):
    """Create pseudo beta features."""
    is_gly = torch.eq(aatype, rc.restype_order["G"])
    ca_idx = rc.atom_order["CA"]
    cb_idx = rc.atom_order["CB"]
    pseudo_beta = torch.where(
        torch.tile(is_gly[..., None], [1] * len(is_gly.shape) + [3]),
        all_atom_positions[..., ca_idx, :],
        all_atom_positions[..., cb_idx, :],
    )

    if all_atom_mask is not None:
        pseudo_beta_mask = torch.where(
            is_gly, all_atom_mask[..., ca_idx], all_atom_mask[..., cb_idx]
        )
        return pseudo_beta, pseudo_beta_mask
    else:
        return pseudo_beta


@curry1
def make_pseudo_beta(protein, prefix=""):
    """Create pseudo-beta (alpha for glycine) position and mask."""
    assert prefix in ["", "template_"]
    (
        protein[prefix + "pseudo_beta"],
        protein[prefix + "pseudo_beta_mask"],
    ) = pseudo_beta_fn(
        protein["template_aatype" if prefix else "aatype"],
        protein[prefix + "all_atom_positions"],
        protein["template_all_atom_mask" if prefix else "all_atom_mask"],
    )
    return protein


@curry1
def add_constant_field(protein, key, value):
    protein[key] = torch.tensor(value, device=protein["msa"].device)
    return protein


def shaped_categorical(probs, epsilon=1e-10):
    ds = probs.shape
    num_classes = ds[-1]
    distribution = torch.distributions.categorical.Categorical(
        torch.reshape(probs + epsilon, [-1, num_classes])
    )
    counts = distribution.sample()
    return torch.reshape(counts, ds[:-1])


def make_hhblits_profile(protein):
    """Compute the HHblits MSA profile if not already present."""
    if "hhblits_profile" in protein:
        return protein

    # Compute the profile for every residue (over all MSA sequences).
    msa_one_hot = make_one_hot(protein["msa"], 22)

    protein["hhblits_profile"] = torch.mean(msa_one_hot, dim=0)
    return protein


@curry1
def make_masked_msa(protein, config, replace_fraction):
    """Create data for BERT on raw MSA."""
    # Add a random amino acid uniformly.
    random_aa = torch.tensor(
        [0.05] * 20 + [0.0, 0.0], 
        dtype=torch.float32, 
        device=protein["aatype"].device
    )

    categorical_probs = (
        config.uniform_prob * random_aa
        + config.profile_prob * protein["hhblits_profile"]
        + config.same_prob * make_one_hot(protein["msa"], 22)
    )

    # Put all remaining probability on [MASK] which is a new column
    pad_shapes = list(
        reduce(add, [(0, 0) for _ in range(len(categorical_probs.shape))])
    )
    pad_shapes[1] = 1
    mask_prob = (
        1.0 - config.profile_prob - config.same_prob - config.uniform_prob
    )
    assert mask_prob >= 0.0

    categorical_probs = torch.nn.functional.pad(
        categorical_probs, pad_shapes, value=mask_prob
    )

    sh = protein["msa"].shape
    mask_position = torch.rand(sh) < replace_fraction

    bert_msa = shaped_categorical(categorical_probs)
    bert_msa = torch.where(mask_position, bert_msa, protein["msa"])

    # Mix real and masked MSA
    protein["bert_mask"] = mask_position.to(torch.float32)
    protein["true_msa"] = protein["msa"]
    protein["msa"] = bert_msa

    return protein


@curry1
def make_fixed_size(
    protein,
    shape_schema,
    msa_cluster_size,
    extra_msa_size,
    num_res=0,
    num_templates=0,
):
    """Guess at the MSA and sequence dimension to make fixed size."""
    pad_size_map = {
        NUM_RES: num_res,
        NUM_MSA_SEQ: msa_cluster_size,
        NUM_EXTRA_SEQ: extra_msa_size,
        NUM_TEMPLATES: num_templates,
    }

    for k, v in protein.items():
        # Don't transfer this to the accelerator.
        if k == "extra_cluster_assignment":
            continue
        shape = list(v.shape)
        schema = shape_schema[k]
        msg = "Rank mismatch between shape and shape schema for"
        assert len(shape) == len(schema), f"{msg} {k}: {shape} vs {schema}"
        pad_size = [
            pad_size_map.get(s2, None) or s1 for (s1, s2) in zip(shape, schema)
        ]

        padding = [(0, p - v.shape[i]) for i, p in enumerate(pad_size)]
        padding.reverse()
        padding = list(itertools.chain(*padding))
        if padding:
            protein[k] = torch.nn.functional.pad(v, padding)
            protein[k] = torch.reshape(protein[k], pad_size)
    
    return protein


@curry1
def make_msa_feat(protein):
    """Create and concatenate MSA features."""
    # Whether there is a domain break. Always zero for chains, but keeping for
    # compatibility with domain datasets.
    has_break = torch.clip(
        protein["between_segment_residues"].to(torch.float32), 0, 1
    )
    aatype_1hot = make_one_hot(protein["aatype"], 21)

    target_feat = [
        torch.unsqueeze(has_break, dim=-1),
        aatype_1hot,  # Everyone gets the original sequence.
    ]

    msa_1hot = make_one_hot(protein["msa"], 23)
    has_deletion = torch.clip(protein["deletion_matrix"], 0.0, 1.0)
    deletion_value = torch.atan(protein["deletion_matrix"] / 3.0) * (
        2.0 / np.pi
    )

    msa_feat = [
        msa_1hot,
        torch.unsqueeze(has_deletion, dim=-1),
        torch.unsqueeze(deletion_value, dim=-1),
    ]

    if "cluster_profile" in protein:
        deletion_mean_value = torch.atan(
            protein["cluster_deletion_mean"] / 3.0
        ) * (2.0 / np.pi)
        msa_feat.extend(
            [
                protein["cluster_profile"],
                torch.unsqueeze(deletion_mean_value, dim=-1),
            ]
        )

    if "extra_deletion_matrix" in protein:
        protein["extra_has_deletion"] = torch.clip(
            protein["extra_deletion_matrix"], 0.0, 1.0
        )
        protein["extra_deletion_value"] = torch.atan(
            protein["extra_deletion_matrix"] / 3.0
        ) * (2.0 / np.pi)

    protein["msa_feat"] = torch.cat(msa_feat, dim=-1)
    protein["target_feat"] = torch.cat(target_feat, dim=-1)
    return protein


@curry1
def select_feat(protein, feature_list):
    return {k: v for k, v in protein.items() if k in feature_list}


@curry1
def crop_templates(protein, max_templates):
    for k, v in protein.items():
        if k.startswith("template_"):
            protein[k] = v[:max_templates]
    return protein


def make_atom14_masks(protein):
    """Construct denser atom positions (14 dimensions instead of 37)."""
    restype_atom14_to_atom37 = []
    restype_atom37_to_atom14 = []
    restype_atom14_mask = []

    for rt in rc.restypes:
        atom_names = rc.restype_name_to_atom14_names[rc.restype_1to3[rt]]
        restype_atom14_to_atom37.append(
            [(rc.atom_order[name] if name else 0) for name in atom_names]
        )
        atom_name_to_idx14 = {name: i for i, name in enumerate(atom_names)}
        restype_atom37_to_atom14.append(
            [
                (atom_name_to_idx14[name] if name in atom_name_to_idx14 else 0)
                for name in rc.atom_types
            ]
        )

        restype_atom14_mask.append(
            [(1.0 if name else 0.0) for name in atom_names]
        )

    # Add dummy mapping for restype 'UNK'
    restype_atom14_to_atom37.append([0] * 14)
    restype_atom37_to_atom14.append([0] * 37)
    restype_atom14_mask.append([0.0] * 14)

    restype_atom14_to_atom37 = torch.tensor(
        restype_atom14_to_atom37,
        dtype=torch.int32,
        device=protein["aatype"].device,
    )
    restype_atom37_to_atom14 = torch.tensor(
        restype_atom37_to_atom14,
        dtype=torch.int32,
        device=protein["aatype"].device,
    )
    restype_atom14_mask = torch.tensor(
        restype_atom14_mask,
        dtype=torch.float32,
        device=protein["aatype"].device,
    )
    protein_aatype = protein['aatype'].to(torch.long)

    # create the mapping for (residx, atom14) --> atom37, i.e. an array
    # with shape (num_res, 14) containing the atom37 indices for this protein
    residx_atom14_to_atom37 = restype_atom14_to_atom37[protein_aatype]
    residx_atom14_mask = restype_atom14_mask[protein_aatype]

    protein["atom14_atom_exists"] = residx_atom14_mask
    protein["residx_atom14_to_atom37"] = residx_atom14_to_atom37.long()

    # create the gather indices for mapping back
    residx_atom37_to_atom14 = restype_atom37_to_atom14[protein_aatype]
    protein["residx_atom37_to_atom14"] = residx_atom37_to_atom14.long()

    # create the corresponding mask
    restype_atom37_mask = torch.zeros(
        [21, 37], dtype=torch.float32, device=protein["aatype"].device
    )
    for restype, restype_letter in enumerate(rc.restypes):
        restype_name = rc.restype_1to3[restype_letter]
        atom_names = rc.residue_atoms[restype_name]
        for atom_name in atom_names:
            atom_type = rc.atom_order[atom_name]
            restype_atom37_mask[restype, atom_type] = 1

    residx_atom37_mask = restype_atom37_mask[protein_aatype]
    protein["atom37_atom_exists"] = residx_atom37_mask

    return protein


def make_atom14_masks_np(batch):
    batch = tree_map(
        lambda n: torch.tensor(n, device=batch["aatype"].device), 
        batch, 
        np.ndarray
    )
    out = make_atom14_masks(batch)
    out = tensor_tree_map(lambda t: np.array(t), out)
    return out


def make_atom14_positions(protein):
    """Constructs denser atom positions (14 dimensions instead of 37)."""
    residx_atom14_mask = protein["atom14_atom_exists"]
    residx_atom14_to_atom37 = protein["residx_atom14_to_atom37"]

    # Create a mask for known ground truth positions.
    residx_atom14_gt_mask = residx_atom14_mask * batched_gather(
        protein["all_atom_mask"],
        residx_atom14_to_atom37,
        dim=-1,
        no_batch_dims=len(protein["all_atom_mask"].shape[:-1]),
    )

    # Gather the ground truth positions.
    residx_atom14_gt_positions = residx_atom14_gt_mask[..., None] * (
        batched_gather(
            protein["all_atom_positions"],
            residx_atom14_to_atom37,
            dim=-2,
            no_batch_dims=len(protein["all_atom_positions"].shape[:-2]),
        )
    )

    protein["atom14_atom_exists"] = residx_atom14_mask
    protein["atom14_gt_exists"] = residx_atom14_gt_mask
    protein["atom14_gt_positions"] = residx_atom14_gt_positions

    # As the atom naming is ambiguous for 7 of the 20 amino acids, provide
    # alternative ground truth coordinates where the naming is swapped
    restype_3 = [rc.restype_1to3[res] for res in rc.restypes]
    restype_3 += ["UNK"]

    # Matrices for renaming ambiguous atoms.
    all_matrices = {
        res: torch.eye(
            14,
            dtype=protein["all_atom_mask"].dtype,
            device=protein["all_atom_mask"].device,
        )
        for res in restype_3
    }
    for resname, swap in rc.residue_atom_renaming_swaps.items():
        correspondences = torch.arange(
            14, device=protein["all_atom_mask"].device
        )
        for source_atom_swap, target_atom_swap in swap.items():
            source_index = rc.restype_name_to_atom14_names[resname].index(
                source_atom_swap
            )
            target_index = rc.restype_name_to_atom14_names[resname].index(
                target_atom_swap
            )
            correspondences[source_index] = target_index
            correspondences[target_index] = source_index
            renaming_matrix = protein["all_atom_mask"].new_zeros((14, 14))
            for index, correspondence in enumerate(correspondences):
                renaming_matrix[index, correspondence] = 1.0
        all_matrices[resname] = renaming_matrix
    
    renaming_matrices = torch.stack(
        [all_matrices[restype] for restype in restype_3]
    )

    # Pick the transformation matrices for the given residue sequence
    # shape (num_res, 14, 14).
    renaming_transform = renaming_matrices[protein["aatype"]]

    # Apply it to the ground truth positions. shape (num_res, 14, 3).
    alternative_gt_positions = torch.einsum(
        "...rac,...rab->...rbc", residx_atom14_gt_positions, renaming_transform
    )
    protein["atom14_alt_gt_positions"] = alternative_gt_positions

    # Create the mask for the alternative ground truth (differs from the
    # ground truth mask, if only one of the atoms in an ambiguous pair has a
    # ground truth position).
    alternative_gt_mask = torch.einsum(
        "...ra,...rab->...rb", residx_atom14_gt_mask, renaming_transform
    )
    protein["atom14_alt_gt_exists"] = alternative_gt_mask

    # Create an ambiguous atoms mask.  shape: (21, 14).
    restype_atom14_is_ambiguous = protein["all_atom_mask"].new_zeros((21, 14))
    for resname, swap in rc.residue_atom_renaming_swaps.items():
        for atom_name1, atom_name2 in swap.items():
            restype = rc.restype_order[rc.restype_3to1[resname]]
            atom_idx1 = rc.restype_name_to_atom14_names[resname].index(
                atom_name1
            )
            atom_idx2 = rc.restype_name_to_atom14_names[resname].index(
                atom_name2
            )
            restype_atom14_is_ambiguous[restype, atom_idx1] = 1
            restype_atom14_is_ambiguous[restype, atom_idx2] = 1

    # From this create an ambiguous_mask for the given sequence.
    protein["atom14_atom_is_ambiguous"] = restype_atom14_is_ambiguous[
        protein["aatype"]
    ]

    return protein


def atom37_to_frames(protein, eps=1e-8):
    aatype = protein["aatype"]
    all_atom_positions = protein["all_atom_positions"]
    all_atom_mask = protein["all_atom_mask"]

    batch_dims = len(aatype.shape[:-1])

    restype_rigidgroup_base_atom_names = np.full([21, 8, 3], "", dtype=object)
    restype_rigidgroup_base_atom_names[:, 0, :] = ["C", "CA", "N"]
    restype_rigidgroup_base_atom_names[:, 3, :] = ["CA", "C", "O"]

    for restype, restype_letter in enumerate(rc.restypes):
        resname = rc.restype_1to3[restype_letter]
        for chi_idx in range(4):
            if rc.chi_angles_mask[restype][chi_idx]:
                names = rc.chi_angles_atoms[resname][chi_idx]
                restype_rigidgroup_base_atom_names[
                    restype, chi_idx + 4, :
                ] = names[1:]

    restype_rigidgroup_mask = all_atom_mask.new_zeros(
        (*aatype.shape[:-1], 21, 8),
    )
    restype_rigidgroup_mask[..., 0] = 1
    restype_rigidgroup_mask[..., 3] = 1
    restype_rigidgroup_mask[..., :20, 4:] = all_atom_mask.new_tensor(
        rc.chi_angles_mask
    )

    lookuptable = rc.atom_order.copy()
    lookuptable[""] = 0
    lookup = np.vectorize(lambda x: lookuptable[x])
    restype_rigidgroup_base_atom37_idx = lookup(
        restype_rigidgroup_base_atom_names,
    )
    restype_rigidgroup_base_atom37_idx = aatype.new_tensor(
        restype_rigidgroup_base_atom37_idx,
    )
    restype_rigidgroup_base_atom37_idx = (
        restype_rigidgroup_base_atom37_idx.view(
            *((1,) * batch_dims), *restype_rigidgroup_base_atom37_idx.shape
        )
    )

    residx_rigidgroup_base_atom37_idx = batched_gather(
        restype_rigidgroup_base_atom37_idx,
        aatype,
        dim=-3,
        no_batch_dims=batch_dims,
    )

    base_atom_pos = batched_gather(
        all_atom_positions,
        residx_rigidgroup_base_atom37_idx,
        dim=-2,
        no_batch_dims=len(all_atom_positions.shape[:-2]),
    )

    gt_frames = Rigid.from_3_points(
        p_neg_x_axis=base_atom_pos[..., 0, :],
        origin=base_atom_pos[..., 1, :],
        p_xy_plane=base_atom_pos[..., 2, :],
        eps=eps,
    )

    group_exists = batched_gather(
        restype_rigidgroup_mask,
        aatype,
        dim=-2,
        no_batch_dims=batch_dims,
    )

    gt_atoms_exist = batched_gather(
        all_atom_mask,
        residx_rigidgroup_base_atom37_idx,
        dim=-1,
        no_batch_dims=len(all_atom_mask.shape[:-1]),
    )
    gt_exists = torch.min(gt_atoms_exist, dim=-1)[0] * group_exists

    rots = torch.eye(3, dtype=all_atom_mask.dtype, device=aatype.device)
    rots = torch.tile(rots, (*((1,) * batch_dims), 8, 1, 1))
    rots[..., 0, 0, 0] = -1
    rots[..., 0, 2, 2] = -1
    rots = Rotation(rot_mats=rots)

    gt_frames = gt_frames.compose(Rigid(rots, None))

    restype_rigidgroup_is_ambiguous = all_atom_mask.new_zeros(
        *((1,) * batch_dims), 21, 8
    )
    restype_rigidgroup_rots = torch.eye(
        3, dtype=all_atom_mask.dtype, device=aatype.device
    )
    restype_rigidgroup_rots = torch.tile(
        restype_rigidgroup_rots,
        (*((1,) * batch_dims), 21, 8, 1, 1),
    )

    for resname, _ in rc.residue_atom_renaming_swaps.items():
        restype = rc.restype_order[rc.restype_3to1[resname]]
        chi_idx = int(sum(rc.chi_angles_mask[restype]) - 1)
        restype_rigidgroup_is_ambiguous[..., restype, chi_idx + 4] = 1
        restype_rigidgroup_rots[..., restype, chi_idx + 4, 1, 1] = -1
        restype_rigidgroup_rots[..., restype, chi_idx + 4, 2, 2] = -1

    residx_rigidgroup_is_ambiguous = batched_gather(
        restype_rigidgroup_is_ambiguous,
        aatype,
        dim=-2,
        no_batch_dims=batch_dims,
    )

    residx_rigidgroup_ambiguity_rot = batched_gather(
        restype_rigidgroup_rots,
        aatype,
        dim=-4,
        no_batch_dims=batch_dims,
    )

    residx_rigidgroup_ambiguity_rot = Rotation(
        rot_mats=residx_rigidgroup_ambiguity_rot
    )
    alt_gt_frames = gt_frames.compose(
        Rigid(residx_rigidgroup_ambiguity_rot, None)
    )

    gt_frames_tensor = gt_frames.to_tensor_4x4()
    alt_gt_frames_tensor = alt_gt_frames.to_tensor_4x4()

    protein["rigidgroups_gt_frames"] = gt_frames_tensor
    protein["rigidgroups_gt_exists"] = gt_exists
    protein["rigidgroups_group_exists"] = group_exists
    protein["rigidgroups_group_is_ambiguous"] = residx_rigidgroup_is_ambiguous
    protein["rigidgroups_alt_gt_frames"] = alt_gt_frames_tensor

    return protein


def get_chi_atom_indices():
    """Returns atom indices needed to compute chi angles for all residue types.

    Returns:
      A tensor of shape [residue_types=21, chis=4, atoms=4]. The residue types are
      in the order specified in rc.restypes + unknown residue type
      at the end. For chi angles which are not defined on the residue, the
      positions indices are by default set to 0.
    """
    chi_atom_indices = []
    for residue_name in rc.restypes:
        residue_name = rc.restype_1to3[residue_name]
        residue_chi_angles = rc.chi_angles_atoms[residue_name]
        atom_indices = []
        for chi_angle in residue_chi_angles:
            atom_indices.append([rc.atom_order[atom] for atom in chi_angle])
        for _ in range(4 - len(atom_indices)):
            atom_indices.append(
                [0, 0, 0, 0]
            )  # For chi angles not defined on the AA.
        chi_atom_indices.append(atom_indices)

    chi_atom_indices.append([[0, 0, 0, 0]] * 4)  # For UNKNOWN residue.

    return chi_atom_indices


@curry1
def atom37_to_torsion_angles(
    protein,
    prefix="",
):
    """
    Convert coordinates to torsion angles.

    This function is extremely sensitive to floating point imprecisions
    and should be run with double precision whenever possible.

    Args:
        Dict containing:
            * (prefix)aatype:
                [*, N_res] residue indices
            * (prefix)all_atom_positions:
                [*, N_res, 37, 3] atom positions (in atom37
                format)
            * (prefix)all_atom_mask:
                [*, N_res, 37] atom position mask
    Returns:
        The same dictionary updated with the following features:

        "(prefix)torsion_angles_sin_cos" ([*, N_res, 7, 2])
            Torsion angles
        "(prefix)alt_torsion_angles_sin_cos" ([*, N_res, 7, 2])
            Alternate torsion angles (accounting for 180-degree symmetry)
        "(prefix)torsion_angles_mask" ([*, N_res, 7])
            Torsion angles mask
    """
    aatype = protein[prefix + "aatype"]
    all_atom_positions = protein[prefix + "all_atom_positions"]
    all_atom_mask = protein[prefix + "all_atom_mask"]

    aatype = torch.clamp(aatype, max=20)

    pad = all_atom_positions.new_zeros(
        [*all_atom_positions.shape[:-3], 1, 37, 3]
    )
    prev_all_atom_positions = torch.cat(
        [pad, all_atom_positions[..., :-1, :, :]], dim=-3
    )

    pad = all_atom_mask.new_zeros([*all_atom_mask.shape[:-2], 1, 37])
    prev_all_atom_mask = torch.cat([pad, all_atom_mask[..., :-1, :]], dim=-2)

    pre_omega_atom_pos = torch.cat(
        [prev_all_atom_positions[..., 1:3, :], all_atom_positions[..., :2, :]],
        dim=-2,
    )
    phi_atom_pos = torch.cat(
        [prev_all_atom_positions[..., 2:3, :], all_atom_positions[..., :3, :]],
        dim=-2,
    )
    psi_atom_pos = torch.cat(
        [all_atom_positions[..., :3, :], all_atom_positions[..., 4:5, :]],
        dim=-2,
    )

    pre_omega_mask = torch.prod(
        prev_all_atom_mask[..., 1:3], dim=-1
    ) * torch.prod(all_atom_mask[..., :2], dim=-1)
    phi_mask = prev_all_atom_mask[..., 2] * torch.prod(
        all_atom_mask[..., :3], dim=-1, dtype=all_atom_mask.dtype
    )
    psi_mask = (
        torch.prod(all_atom_mask[..., :3], dim=-1, dtype=all_atom_mask.dtype)
        * all_atom_mask[..., 4]
    )

    chi_atom_indices = torch.as_tensor(
        get_chi_atom_indices(), device=aatype.device
    )

    atom_indices = chi_atom_indices[..., aatype, :, :]
    chis_atom_pos = batched_gather(
        all_atom_positions, atom_indices, -2, len(atom_indices.shape[:-2])
    )

    chi_angles_mask = list(rc.chi_angles_mask)
    chi_angles_mask.append([0.0, 0.0, 0.0, 0.0])
    chi_angles_mask = all_atom_mask.new_tensor(chi_angles_mask)

    chis_mask = chi_angles_mask[aatype, :]

    chi_angle_atoms_mask = batched_gather(
        all_atom_mask,
        atom_indices,
        dim=-1,
        no_batch_dims=len(atom_indices.shape[:-2]),
    )
    chi_angle_atoms_mask = torch.prod(
        chi_angle_atoms_mask, dim=-1, dtype=chi_angle_atoms_mask.dtype
    )
    chis_mask = chis_mask * chi_angle_atoms_mask

    torsions_atom_pos = torch.cat(
        [
            pre_omega_atom_pos[..., None, :, :],
            phi_atom_pos[..., None, :, :],
            psi_atom_pos[..., None, :, :],
            chis_atom_pos,
        ],
        dim=-3,
    )

    torsion_angles_mask = torch.cat(
        [
            pre_omega_mask[..., None],
            phi_mask[..., None],
            psi_mask[..., None],
            chis_mask,
        ],
        dim=-1,
    )

    torsion_frames = Rigid.from_3_points(
        torsions_atom_pos[..., 1, :],
        torsions_atom_pos[..., 2, :],
        torsions_atom_pos[..., 0, :],
        eps=1e-8,
    )

    fourth_atom_rel_pos = torsion_frames.invert().apply(
        torsions_atom_pos[..., 3, :]
    )

    torsion_angles_sin_cos = torch.stack(
        [fourth_atom_rel_pos[..., 2], fourth_atom_rel_pos[..., 1]], dim=-1
    )

    denom = torch.sqrt(
        torch.sum(
            torch.square(torsion_angles_sin_cos),
            dim=-1,
            dtype=torsion_angles_sin_cos.dtype,
            keepdims=True,
        )
        + 1e-8
    )
    torsion_angles_sin_cos = torsion_angles_sin_cos / denom

    torsion_angles_sin_cos = torsion_angles_sin_cos * all_atom_mask.new_tensor(
        [1.0, 1.0, -1.0, 1.0, 1.0, 1.0, 1.0],
    )[((None,) * len(torsion_angles_sin_cos.shape[:-2])) + (slice(None), None)]

    chi_is_ambiguous = torsion_angles_sin_cos.new_tensor(
        rc.chi_pi_periodic,
    )[aatype, ...]

    mirror_torsion_angles = torch.cat(
        [
            all_atom_mask.new_ones(*aatype.shape, 3),
            1.0 - 2.0 * chi_is_ambiguous,
        ],
        dim=-1,
    )

    alt_torsion_angles_sin_cos = (
        torsion_angles_sin_cos * mirror_torsion_angles[..., None]
    )

    protein[prefix + "torsion_angles_sin_cos"] = torsion_angles_sin_cos
    protein[prefix + "alt_torsion_angles_sin_cos"] = alt_torsion_angles_sin_cos
    protein[prefix + "torsion_angles_mask"] = torsion_angles_mask

    return protein


def get_backbone_frames(protein):
    # DISCREPANCY: AlphaFold uses tensor_7s here. I don't know why.
    protein["backbone_rigid_tensor"] = protein["rigidgroups_gt_frames"][
        ..., 0, :, :
    ]
    protein["backbone_rigid_mask"] = protein["rigidgroups_gt_exists"][..., 0]

    return protein


def get_chi_angles(protein):
    dtype = protein["all_atom_mask"].dtype
    protein["chi_angles_sin_cos"] = (
        protein["torsion_angles_sin_cos"][..., 3:, :]
    ).to(dtype)
    protein["chi_mask"] = protein["torsion_angles_mask"][..., 3:].to(dtype)

    return protein


@curry1
def random_crop_to_size(
    protein,
    crop_size,
    max_templates,
    shape_schema,
    subsample_templates=False,
    seed=None,
):
    """Crop randomly to `crop_size`, or keep as is if shorter than that."""
    # We want each ensemble to be cropped the same way
    g = torch.Generator(device=protein["seq_length"].device)
    if seed is not None:
        g.manual_seed(seed)

    seq_length = protein["seq_length"]

    if "template_mask" in protein:
        num_templates = protein["template_mask"].shape[-1]
    else:
        num_templates = 0

    # No need to subsample templates if there aren't any
    subsample_templates = subsample_templates and num_templates

    num_res_crop_size = min(int(seq_length), crop_size)

    def _randint(lower, upper):
        return int(torch.randint(
                lower,
                upper + 1,
                (1,),
                device=protein["seq_length"].device,
                generator=g,
        )[0])

    if subsample_templates:
        templates_crop_start = _randint(0, num_templates)
        templates_select_indices = torch.randperm(
            num_templates, device=protein["seq_length"].device, generator=g
        )
    else:
        templates_crop_start = 0

    num_templates_crop_size = min(
        num_templates - templates_crop_start, max_templates
    )

    n = seq_length - num_res_crop_size
    if "use_clamped_fape" in protein and protein["use_clamped_fape"] == 1.:
        right_anchor = n
    else:
        x = _randint(0, n)
        right_anchor = n - x

    num_res_crop_start = _randint(0, right_anchor)

    for k, v in protein.items():
        if k not in shape_schema or (
            "template" not in k and NUM_RES not in shape_schema[k]
        ):
            continue

        # randomly permute the templates before cropping them.
        if k.startswith("template") and subsample_templates:
            v = v[templates_select_indices]

        slices = []
        for i, (dim_size, dim) in enumerate(zip(shape_schema[k], v.shape)):
            is_num_res = dim_size == NUM_RES
            if i == 0 and k.startswith("template"):
                crop_size = num_templates_crop_size
                crop_start = templates_crop_start
            else:
                crop_start = num_res_crop_start if is_num_res else 0
                crop_size = num_res_crop_size if is_num_res else dim
            slices.append(slice(crop_start, crop_start + crop_size))
        protein[k] = v[slices]

    protein["seq_length"] = protein["seq_length"].new_tensor(num_res_crop_size)
    
    return protein