add prototype dataset for CelebA (#4514)

* add prototype dataset for CelebA

* fix code format

* fix mypy

* hardcode fmtparams

* fix mypy

* replace KeyZipper with Zipper for annotations

torchvision/prototype/datasets/_builtin/__init__.py

 from .caltech import Caltech101, Caltech256
+from .celeba import CelebA
 from .cifar import Cifar10, Cifar100
 from .sbd import SBD
 from .voc import VOC

torchvision/prototype/datasets/_builtin/celeba.py

+import csv
+import io
+from typing import Any, Callable, Dict, List, Optional, Tuple, Mapping, Union
+
+import torch
+from torch.utils.data import IterDataPipe
+from torch.utils.data.datapipes.iter import (
+    Mapper,
+    Shuffler,
+    Filter,
+    ZipArchiveReader,
+    Zipper,
+)
+from torchdata.datapipes.iter import KeyZipper
+from torchvision.prototype.datasets.utils import (
+    Dataset,
+    DatasetConfig,
+    DatasetInfo,
+    GDriveResource,
+    OnlineResource,
+    DatasetType,
+)
+from torchvision.prototype.datasets.utils._internal import INFINITE_BUFFER_SIZE, getitem, path_accessor
+
+
+class CelebACSVParser(IterDataPipe):
+    def __init__(
+        self,
+        datapipe,
+        *,
+        has_header,
+    ):
+        self.datapipe = datapipe
+        self.has_header = has_header
+        self._fmtparams = dict(delimiter=" ", skipinitialspace=True)
+
+    def __iter__(self):
+        for _, file in self.datapipe:
+            file = (line.decode() for line in file)
+
+            if self.has_header:
+                # The first row is skipped, because it only contains the number of samples
+                next(file)
+
+                # Empty field names are filtered out, because some files have an extr white space after the header
+                # line, which is recognized as extra column
+                fieldnames = [name for name in next(csv.reader([next(file)], **self._fmtparams)) if name]
+                # Some files do not include a label for the image ID column
+                if fieldnames[0] != "image_id":
+                    fieldnames.insert(0, "image_id")
+
+                for line in csv.DictReader(file, fieldnames=fieldnames, **self._fmtparams):
+                    yield line.pop("image_id"), line
+            else:
+                for line in csv.reader(file, **self._fmtparams):
+                    yield line[0], line[1:]
+
+
+class CelebA(Dataset):
+    @property
+    def info(self) -> DatasetInfo:
+        return DatasetInfo(
+            "celeba",
+            type=DatasetType.IMAGE,
+            homepage="https://mmlab.ie.cuhk.edu.hk/projects/CelebA.html",
+        )
+
+    def resources(self, config: DatasetConfig) -> List[OnlineResource]:
+        splits = GDriveResource(
+            "0B7EVK8r0v71pY0NSMzRuSXJEVkk",
+            sha256="fc955bcb3ef8fbdf7d5640d9a8693a8431b5f2ee291a5c1449a1549e7e073fe7",
+            file_name="list_eval_partition.txt",
+        )
+        images = GDriveResource(
+            "0B7EVK8r0v71pZjFTYXZWM3FlRnM",
+            sha256="46fb89443c578308acf364d7d379fe1b9efb793042c0af734b6112e4fd3a8c74",
+            file_name="img_align_celeba.zip",
+        )
+        identities = GDriveResource(
+            "1_ee_0u7vcNLOfNLegJRHmolfH5ICW-XS",
+            sha256="c6143857c3e2630ac2da9f782e9c1232e5e59be993a9d44e8a7916c78a6158c0",
+            file_name="identity_CelebA.txt",
+        )
+        attributes = GDriveResource(
+            "0B7EVK8r0v71pblRyaVFSWGxPY0U",
+            sha256="f0e5da289d5ccf75ffe8811132694922b60f2af59256ed362afa03fefba324d0",
+            file_name="list_attr_celeba.txt",
+        )
+        bboxes = GDriveResource(
+            "0B7EVK8r0v71pbThiMVRxWXZ4dU0",
+            sha256="7487a82e57c4bb956c5445ae2df4a91ffa717e903c5fa22874ede0820c8ec41b",
+            file_name="list_bbox_celeba.txt",
+        )
+        landmarks = GDriveResource(
+            "0B7EVK8r0v71pd0FJY3Blby1HUTQ",
+            sha256="6c02a87569907f6db2ba99019085697596730e8129f67a3d61659f198c48d43b",
+            file_name="list_landmarks_align_celeba.txt",
+        )
+        return [splits, images, identities, attributes, bboxes, landmarks]
+
+    _SPLIT_ID_TO_NAME = {
+        "0": "train",
+        "1": "valid",
+        "2": "test",
+    }
+
+    def _filter_split(self, data: Tuple[str, str], *, split):
+        _, split_id = data
+        return self._SPLIT_ID_TO_NAME[split_id[0]] == split
+
+    def _collate_anns(
+        self, data: Tuple[Tuple[str, Union[List[str], Mapping[str, str]]], ...]
+    ) -> Tuple[str, Dict[str, Union[List[str], Mapping[str, str]]]]:
+        (image_id, identity), (_, attributes), (_, bbox), (_, landmarks) = data
+        return image_id, dict(identity=identity, attributes=attributes, bbox=bbox, landmarks=landmarks)
+
+    def _collate_and_decode_sample(
+        self,
+        data: Tuple[Tuple[str, Tuple[str, List[str]], Tuple[str, io.IOBase]], Tuple[str, Dict[str, Any]]],
+        *,
+        decoder: Optional[Callable[[io.IOBase], torch.Tensor]],
+    ) -> Dict[str, Any]:
+        split_and_image_data, ann_data = data
+        _, _, image_data = split_and_image_data
+        path, buffer = image_data
+        _, ann = ann_data
+
+        image = decoder(buffer) if decoder else buffer
+
+        identity = torch.tensor(int(ann["identity"][0]))
+        attributes = {attr: value == "1" for attr, value in ann["attributes"].items()}
+        bbox = torch.tensor([int(ann["bbox"][key]) for key in ("x_1", "y_1", "width", "height")])
+        landmarks = {
+            landmark: torch.tensor((int(ann["landmarks"][f"{landmark}_x"]), int(ann["landmarks"][f"{landmark}_y"])))
+            for landmark in {key[:-2] for key in ann["landmarks"].keys()}
+        }
+
+        return dict(
+            path=path,
+            image=image,
+            identity=identity,
+            attributes=attributes,
+            bbox=bbox,
+            landmarks=landmarks,
+        )
+
+    def _make_datapipe(
+        self,
+        resource_dps: List[IterDataPipe],
+        *,
+        config: DatasetConfig,
+        decoder: Optional[Callable[[io.IOBase], torch.Tensor]],
+    ) -> IterDataPipe[Dict[str, Any]]:
+        splits_dp, images_dp, identities_dp, attributes_dp, bboxes_dp, landmarks_dp = resource_dps
+
+        splits_dp = CelebACSVParser(splits_dp, has_header=False)
+        splits_dp: IterDataPipe = Filter(splits_dp, self._filter_split, fn_kwargs=dict(split=config.split))
+        splits_dp = Shuffler(splits_dp, buffer_size=INFINITE_BUFFER_SIZE)
+
+        images_dp = ZipArchiveReader(images_dp)
+
+        anns_dp: IterDataPipe = Zipper(
+            *[
+                CelebACSVParser(dp, has_header=has_header)
+                for dp, has_header in (
+                    (identities_dp, False),
+                    (attributes_dp, True),
+                    (bboxes_dp, True),
+                    (landmarks_dp, True),
+                )
+            ]
+        )
+        anns_dp: IterDataPipe = Mapper(anns_dp, self._collate_anns)
+
+        dp = KeyZipper(
+            splits_dp,
+            images_dp,
+            key_fn=getitem(0),
+            ref_key_fn=path_accessor("name"),
+            buffer_size=INFINITE_BUFFER_SIZE,
+            keep_key=True,
+        )
+        dp = KeyZipper(dp, anns_dp, key_fn=getitem(0), buffer_size=INFINITE_BUFFER_SIZE)
+        return Mapper(dp, self._collate_and_decode_sample, fn_kwargs=dict(decoder=decoder))