# Copyright 2022 The TensorFlow Authors. All Rights Reserved.
#
# 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.

"""Contains common building blocks for neural networks."""

from typing import Any, Callable, Dict, List, Mapping, Optional, Sequence, Tuple, Union

import tensorflow as tf

import tensorflow_model_optimization as tfmot
from official.modeling import tf_utils
from official.projects.qat.vision.quantization import configs
from official.projects.qat.vision.quantization import helper
from official.vision.modeling.decoders import aspp
from official.vision.modeling.layers import nn_layers


# Type annotations.
States = Dict[str, tf.Tensor]
Activation = Union[str, Callable]


class NoOpActivation:
  """No-op activation which simply returns the incoming tensor.

  This activation is required to distinguish between `keras.activations.linear`
  which does the same thing. The main difference is that NoOpActivation should
  not have any quantize operation applied to it.
  """

  def __call__(self, x: tf.Tensor) -> tf.Tensor:
    return x

  def get_config(self) -> Dict[str, Any]:
    """Get a config of this object."""
    return {}

  def __eq__(self, other: Any) -> bool:
    return isinstance(other, NoOpActivation)

  def __ne__(self, other: Any) -> bool:
    return not self.__eq__(other)


def _quantize_wrapped_layer(cls, quantize_config):
  def constructor(*arg, **kwargs):
    return tfmot.quantization.keras.QuantizeWrapperV2(
        cls(*arg, **kwargs),
        quantize_config)
  return constructor


@tf.keras.utils.register_keras_serializable(package='Vision')
class SqueezeExcitationQuantized(
    helper.LayerQuantizerHelper,
    tf.keras.layers.Layer):
  """Creates a squeeze and excitation layer."""

  def __init__(self,
               in_filters,
               out_filters,
               se_ratio,
               divisible_by=1,
               use_3d_input=False,
               kernel_initializer='VarianceScaling',
               kernel_regularizer=None,
               bias_regularizer=None,
               activation='relu',
               gating_activation='sigmoid',
               round_down_protect=True,
               **kwargs):
    """Initializes a squeeze and excitation layer.

    Args:
      in_filters: An `int` number of filters of the input tensor.
      out_filters: An `int` number of filters of the output tensor.
      se_ratio: A `float` or None. If not None, se ratio for the squeeze and
        excitation layer.
      divisible_by: An `int` that ensures all inner dimensions are divisible by
        this number.
      use_3d_input: A `bool` of whether input is 2D or 3D image.
      kernel_initializer: A `str` of kernel_initializer for convolutional
        layers.
      kernel_regularizer: A `tf.keras.regularizers.Regularizer` object for
        Conv2D. Default to None.
      bias_regularizer: A `tf.keras.regularizers.Regularizer` object for Conv2d.
        Default to None.
      activation: A `str` name of the activation function.
      gating_activation: A `str` name of the activation function for final
        gating function.
      round_down_protect: A `bool` of whether round down more than 10% will be
        allowed.
      **kwargs: Additional keyword arguments to be passed.
    """
    super().__init__(**kwargs)

    self._in_filters = in_filters
    self._out_filters = out_filters
    self._se_ratio = se_ratio
    self._divisible_by = divisible_by
    self._round_down_protect = round_down_protect
    self._use_3d_input = use_3d_input
    self._activation = activation
    self._gating_activation = gating_activation
    self._kernel_initializer = kernel_initializer
    self._kernel_regularizer = kernel_regularizer
    self._bias_regularizer = bias_regularizer
    if tf.keras.backend.image_data_format() == 'channels_last':
      if not use_3d_input:
        self._spatial_axis = [1, 2]
      else:
        self._spatial_axis = [1, 2, 3]
    else:
      if not use_3d_input:
        self._spatial_axis = [2, 3]
      else:
        self._spatial_axis = [2, 3, 4]

  def _create_gating_activation_layer(self):
    if self._gating_activation == 'hard_sigmoid':
      # Convert hard_sigmoid activation to quantizable keras layers so each op
      # can be properly quantized.
      # Formula is hard_sigmoid(x) = relu6(x + 3) * 0.16667.
      self._add_quantizer('add_three')
      self._add_quantizer('divide_six')
      self._relu6 = tfmot.quantization.keras.QuantizeWrapperV2(
          tf_utils.get_activation('relu6', use_keras_layer=True),
          configs.Default8BitActivationQuantizeConfig())
    else:
      self._gating_activation_layer = tfmot.quantization.keras.QuantizeWrapperV2(
          tf_utils.get_activation(
              self._gating_activation, use_keras_layer=True),
          configs.Default8BitActivationQuantizeConfig())

  def _apply_gating_activation_layer(
      self, x: tf.Tensor, training: bool) -> tf.Tensor:
    if self._gating_activation == 'hard_sigmoid':
      x = self._apply_quantizer('add_three', x + 3.0, training)
      x = self._relu6(x)
      x = self._apply_quantizer('divide_six', x * 1.6667, training)
    else:
      x = self._gating_activation_layer(x)
    return x

  def build(self, input_shape):
    conv2d_quantized = _quantize_wrapped_layer(
        tf.keras.layers.Conv2D,
        configs.Default8BitConvQuantizeConfig(
            ['kernel'], ['activation'], False))
    conv2d_quantized_output_quantized = _quantize_wrapped_layer(
        tf.keras.layers.Conv2D,
        configs.Default8BitConvQuantizeConfig(
            ['kernel'], ['activation'], True))
    num_reduced_filters = nn_layers.make_divisible(
        max(1, int(self._in_filters * self._se_ratio)),
        divisor=self._divisible_by,
        round_down_protect=self._round_down_protect)

    self._se_reduce = conv2d_quantized(
        filters=num_reduced_filters,
        kernel_size=1,
        strides=1,
        padding='same',
        use_bias=True,
        kernel_initializer=self._kernel_initializer,
        kernel_regularizer=self._kernel_regularizer,
        bias_regularizer=self._bias_regularizer,
        activation=NoOpActivation())

    self._se_expand = conv2d_quantized_output_quantized(
        filters=self._out_filters,
        kernel_size=1,
        strides=1,
        padding='same',
        use_bias=True,
        kernel_initializer=self._kernel_initializer,
        kernel_regularizer=self._kernel_regularizer,
        bias_regularizer=self._bias_regularizer,
        activation=NoOpActivation())

    self._multiply = tfmot.quantization.keras.QuantizeWrapperV2(
        tf.keras.layers.Multiply(),
        configs.Default8BitQuantizeConfig([], [], True))
    self._reduce_mean_quantizer = (
        tfmot.quantization.keras.quantizers.MovingAverageQuantizer(
            num_bits=8, per_axis=False, symmetric=False, narrow_range=False))
    self._reduce_mean_quantizer_vars = self._reduce_mean_quantizer.build(
        None, 'reduce_mean_quantizer_vars', self)

    self._activation_layer = tfmot.quantization.keras.QuantizeWrapperV2(
        tf_utils.get_activation(self._activation, use_keras_layer=True),
        configs.Default8BitActivationQuantizeConfig())
    self._create_gating_activation_layer()

    self._build_quantizer_vars()
    super().build(input_shape)

  def get_config(self):
    config = {
        'in_filters': self._in_filters,
        'out_filters': self._out_filters,
        'se_ratio': self._se_ratio,
        'divisible_by': self._divisible_by,
        'use_3d_input': self._use_3d_input,
        'kernel_initializer': self._kernel_initializer,
        'kernel_regularizer': self._kernel_regularizer,
        'bias_regularizer': self._bias_regularizer,
        'activation': self._activation,
        'gating_activation': self._gating_activation,
        'round_down_protect': self._round_down_protect,
    }
    base_config = super().get_config()
    return dict(list(base_config.items()) + list(config.items()))

  def call(self, inputs, training=None):
    x = tf.reduce_mean(inputs, self._spatial_axis, keepdims=True)
    x = self._reduce_mean_quantizer(
        x, training, self._reduce_mean_quantizer_vars)
    x = self._activation_layer(self._se_reduce(x))
    x = self._apply_gating_activation_layer(self._se_expand(x), training)
    x = self._multiply([x, inputs])
    return x


@tf.keras.utils.register_keras_serializable(package='Vision')
class SegmentationHeadQuantized(tf.keras.layers.Layer):
  """Creates a segmentation head."""

  def __init__(
      self,
      num_classes: int,
      level: Union[int, str],
      num_convs: int = 2,
      num_filters: int = 256,
      use_depthwise_convolution: bool = False,
      prediction_kernel_size: int = 1,
      upsample_factor: int = 1,
      feature_fusion: Optional[str] = None,
      decoder_min_level: Optional[int] = None,
      decoder_max_level: Optional[int] = None,
      low_level: int = 2,
      low_level_num_filters: int = 48,
      num_decoder_filters: int = 256,
      activation: str = 'relu',
      use_sync_bn: bool = False,
      norm_momentum: float = 0.99,
      norm_epsilon: float = 0.001,
      kernel_regularizer: Optional[tf.keras.regularizers.Regularizer] = None,
      bias_regularizer: Optional[tf.keras.regularizers.Regularizer] = None,
      **kwargs):
    """Initializes a segmentation head.

    Args:
      num_classes: An `int` number of mask classification categories. The number
        of classes does not include background class.
      level: An `int` or `str`, level to use to build segmentation head.
      num_convs: An `int` number of stacked convolution before the last
        prediction layer.
      num_filters: An `int` number to specify the number of filters used.
        Default is 256.
      use_depthwise_convolution: A bool to specify if use depthwise separable
        convolutions.
      prediction_kernel_size: An `int` number to specify the kernel size of the
        prediction layer.
      upsample_factor: An `int` number to specify the upsampling factor to
        generate finer mask. Default 1 means no upsampling is applied.
      feature_fusion: One of `deeplabv3plus`, `pyramid_fusion`, or None. If
        `deeplabv3plus`, features from decoder_features[level] will be fused
        with low level feature maps from backbone. If `pyramid_fusion`,
        multiscale features will be resized and fused at the target level.
      decoder_min_level: An `int` of minimum level from decoder to use in
        feature fusion. It is only used when feature_fusion is set to
        `panoptic_fpn_fusion`.
      decoder_max_level: An `int` of maximum level from decoder to use in
        feature fusion. It is only used when feature_fusion is set to
        `panoptic_fpn_fusion`.
      low_level: An `int` of backbone level to be used for feature fusion. It is
        used when feature_fusion is set to `deeplabv3plus`.
      low_level_num_filters: An `int` of reduced number of filters for the low
        level features before fusing it with higher level features. It is only
        used when feature_fusion is set to `deeplabv3plus`.
      num_decoder_filters: An `int` of number of filters in the decoder outputs.
        It is only used when feature_fusion is set to `panoptic_fpn_fusion`.
      activation: A `str` that indicates which activation is used, e.g. 'relu',
        'swish', etc.
      use_sync_bn: A `bool` that indicates whether to use synchronized batch
        normalization across different replicas.
      norm_momentum: A `float` of normalization momentum for the moving average.
      norm_epsilon: A `float` added to variance to avoid dividing by zero.
      kernel_regularizer: A `tf.keras.regularizers.Regularizer` object for
        Conv2D. Default is None.
      bias_regularizer: A `tf.keras.regularizers.Regularizer` object for Conv2D.
      **kwargs: Additional keyword arguments to be passed.
    """
    super().__init__(**kwargs)

    self._config_dict = {
        'num_classes': num_classes,
        'level': level,
        'num_convs': num_convs,
        'num_filters': num_filters,
        'use_depthwise_convolution': use_depthwise_convolution,
        'prediction_kernel_size': prediction_kernel_size,
        'upsample_factor': upsample_factor,
        'feature_fusion': feature_fusion,
        'decoder_min_level': decoder_min_level,
        'decoder_max_level': decoder_max_level,
        'low_level': low_level,
        'low_level_num_filters': low_level_num_filters,
        'num_decoder_filters': num_decoder_filters,
        'activation': activation,
        'use_sync_bn': use_sync_bn,
        'norm_momentum': norm_momentum,
        'norm_epsilon': norm_epsilon,
        'kernel_regularizer': kernel_regularizer,
        'bias_regularizer': bias_regularizer,
    }
    if tf.keras.backend.image_data_format() == 'channels_last':
      self._bn_axis = -1
    else:
      self._bn_axis = 1
    self._activation_layer = tfmot.quantization.keras.QuantizeWrapperV2(
        tf_utils.get_activation(activation, use_keras_layer=True),
        configs.Default8BitActivationQuantizeConfig())

  def build(self, input_shape: Sequence[tf.TensorShape]):
    """Creates the variables of the segmentation head."""
    # When input_shape is a list/tuple, the first corresponds to backbone
    # features used for resizing the decoder features (the second) if feature
    # fusion type is `deeplabv3plus`.
    backbone_shape = input_shape[0]
    use_depthwise_convolution = self._config_dict['use_depthwise_convolution']
    random_initializer = tf.keras.initializers.RandomNormal(stddev=0.01)
    conv2d_quantized = _quantize_wrapped_layer(
        tf.keras.layers.Conv2D,
        configs.Default8BitConvQuantizeConfig(['kernel'], ['activation'],
                                              False))
    conv2d_quantized_output_quantized = _quantize_wrapped_layer(
        tf.keras.layers.Conv2D,
        configs.Default8BitConvQuantizeConfig(['kernel'], ['activation'], True))
    depthwise_conv2d_quantized = _quantize_wrapped_layer(
        tf.keras.layers.DepthwiseConv2D,
        configs.Default8BitConvQuantizeConfig(['depthwise_kernel'],
                                              ['activation'], False))
    conv_kwargs = {
        'kernel_size': 3 if not use_depthwise_convolution else 1,
        'padding': 'same',
        'use_bias': False,
        'kernel_initializer': random_initializer,
        'kernel_regularizer': self._config_dict['kernel_regularizer'],
    }

    norm_layer = (
        tf.keras.layers.experimental.SyncBatchNormalization
        if self._config_dict['use_sync_bn'] else
        tf.keras.layers.BatchNormalization)
    norm_with_quantize = _quantize_wrapped_layer(
        norm_layer, configs.Default8BitOutputQuantizeConfig())
    norm = norm_with_quantize if self._config_dict['activation'] not in [
        'relu', 'relu6'
    ] else _quantize_wrapped_layer(norm_layer, configs.NoOpQuantizeConfig())

    bn_kwargs = {
        'axis': self._bn_axis,
        'momentum': self._config_dict['norm_momentum'],
        'epsilon': self._config_dict['norm_epsilon'],
    }

    if self._config_dict['feature_fusion'] == 'deeplabv3plus':
      # Deeplabv3+ feature fusion layers.
      self._dlv3p_conv = conv2d_quantized(
          kernel_size=1,
          padding='same',
          use_bias=False,
          kernel_initializer=tf.keras.initializers.RandomNormal(stddev=0.01),
          kernel_regularizer=self._config_dict['kernel_regularizer'],
          name='segmentation_head_deeplabv3p_fusion_conv',
          filters=self._config_dict['low_level_num_filters'],
          activation=NoOpActivation())

      self._dlv3p_norm = norm(
          name='segmentation_head_deeplabv3p_fusion_norm', **bn_kwargs)

    # Segmentation head layers.
    self._convs = []
    self._norms = []
    for i in range(self._config_dict['num_convs']):
      if use_depthwise_convolution:
        self._convs.append(
            depthwise_conv2d_quantized(
                name='segmentation_head_depthwise_conv_{}'.format(i),
                kernel_size=3,
                padding='same',
                use_bias=False,
                depthwise_initializer=random_initializer,
                depthwise_regularizer=self._config_dict['kernel_regularizer'],
                depth_multiplier=1,
                activation=NoOpActivation()))
        norm_name = 'segmentation_head_depthwise_norm_{}'.format(i)
        self._norms.append(norm(name=norm_name, **bn_kwargs))
      conv_name = 'segmentation_head_conv_{}'.format(i)
      self._convs.append(
          conv2d_quantized(
              name=conv_name,
              filters=self._config_dict['num_filters'],
              activation=NoOpActivation(),
              **conv_kwargs))
      norm_name = 'segmentation_head_norm_{}'.format(i)
      self._norms.append(norm(name=norm_name, **bn_kwargs))

    self._classifier = conv2d_quantized_output_quantized(
        name='segmentation_output',
        filters=self._config_dict['num_classes'],
        kernel_size=self._config_dict['prediction_kernel_size'],
        padding='same',
        bias_initializer=tf.zeros_initializer(),
        kernel_initializer=tf.keras.initializers.RandomNormal(stddev=0.01),
        kernel_regularizer=self._config_dict['kernel_regularizer'],
        bias_regularizer=self._config_dict['bias_regularizer'],
        activation=NoOpActivation())

    upsampling = _quantize_wrapped_layer(
        tf.keras.layers.UpSampling2D,
        configs.Default8BitQuantizeConfig([], [], True))
    self._upsampling_layer = upsampling(
        size=(self._config_dict['upsample_factor'],
              self._config_dict['upsample_factor']),
        interpolation='nearest')
    self._resizing_layer = tf.keras.layers.Resizing(
        backbone_shape[1], backbone_shape[2], interpolation='bilinear')

    concat = _quantize_wrapped_layer(
        tf.keras.layers.Concatenate,
        configs.Default8BitQuantizeConfig([], [], True))
    self._concat_layer = concat(axis=self._bn_axis)

    super().build(input_shape)

  def call(self, inputs: Tuple[Union[tf.Tensor, Mapping[str, tf.Tensor]],
                               Union[tf.Tensor, Mapping[str, tf.Tensor]]]):
    """Forward pass of the segmentation head.

    It supports both a tuple of 2 tensors or 2 dictionaries. The first is
    backbone endpoints, and the second is decoder endpoints. When inputs are
    tensors, they are from a single level of feature maps. When inputs are
    dictionaries, they contain multiple levels of feature maps, where the key
    is the index of feature map.

    Args:
      inputs: A tuple of 2 feature map tensors of shape
        [batch, height_l, width_l, channels] or 2 dictionaries of tensors:
        - key: A `str` of the level of the multilevel features.
        - values: A `tf.Tensor` of the feature map tensors, whose shape is
          [batch, height_l, width_l, channels].

    Returns:
      segmentation prediction mask: A `tf.Tensor` of the segmentation mask
        scores predicted from input features.
    """
    if self._config_dict['feature_fusion'] in ('pyramid_fusion',
                                               'panoptic_fpn_fusion'):
      raise ValueError(
          'The feature fusion method `pyramid_fusion` is not supported in QAT.')

    backbone_output = inputs[0]
    decoder_output = inputs[1]
    if self._config_dict['feature_fusion'] == 'deeplabv3plus':
      # deeplabv3+ feature fusion.
      x = decoder_output[str(self._config_dict['level'])] if isinstance(
          decoder_output, dict) else decoder_output
      y = backbone_output[str(self._config_dict['low_level'])] if isinstance(
          backbone_output, dict) else backbone_output
      y = self._dlv3p_norm(self._dlv3p_conv(y))
      y = self._activation_layer(y)
      x = self._resizing_layer(x)
      x = tf.cast(x, dtype=y.dtype)
      x = self._concat_layer([x, y])
    else:
      x = decoder_output[str(self._config_dict['level'])] if isinstance(
          decoder_output, dict) else decoder_output

    for conv, norm in zip(self._convs, self._norms):
      x = conv(x)
      x = norm(x)
      x = self._activation_layer(x)
    if self._config_dict['upsample_factor'] > 1:
      # Use keras layer for nearest upsampling so it is QAT compatible.
      x = self._upsampling_layer(x)

    return self._classifier(x)

  def get_config(self):
    base_config = super().get_config()
    return dict(list(base_config.items()) + list(self._config_dict.items()))

  @classmethod
  def from_config(cls, config):
    return cls(**config)


@tf.keras.utils.register_keras_serializable(package='Vision')
class SpatialPyramidPoolingQuantized(nn_layers.SpatialPyramidPooling):
  """Implements the quantized Atrous Spatial Pyramid Pooling.

  References:
    [Rethinking Atrous Convolution for Semantic Image Segmentation](
      https://arxiv.org/pdf/1706.05587.pdf)
    [Encoder-Decoder with Atrous Separable Convolution for Semantic Image
    Segmentation](https://arxiv.org/pdf/1802.02611.pdf)
  """

  def __init__(
      self,
      output_channels: int,
      dilation_rates: List[int],
      pool_kernel_size: Optional[List[int]] = None,
      use_sync_bn: bool = False,
      batchnorm_momentum: float = 0.99,
      batchnorm_epsilon: float = 0.001,
      activation: str = 'relu',
      dropout: float = 0.5,
      kernel_initializer: str = 'GlorotUniform',
      kernel_regularizer: Optional[tf.keras.regularizers.Regularizer] = None,
      interpolation: str = 'bilinear',
      use_depthwise_convolution: bool = False,
      **kwargs):
    """Initializes `SpatialPyramidPooling`.

    Args:
      output_channels: Number of channels produced by SpatialPyramidPooling.
      dilation_rates: A list of integers for parallel dilated conv.
      pool_kernel_size: A list of integers or None. If None, global average
        pooling is applied, otherwise an average pooling of pool_kernel_size is
        applied.
      use_sync_bn: A bool, whether or not to use sync batch normalization.
      batchnorm_momentum: A float for the momentum in BatchNorm. Defaults to
        0.99.
      batchnorm_epsilon: A float for the epsilon value in BatchNorm. Defaults to
        0.001.
      activation: A `str` for type of activation to be used. Defaults to 'relu'.
      dropout: A float for the dropout rate before output. Defaults to 0.5.
      kernel_initializer: Kernel initializer for conv layers. Defaults to
        `glorot_uniform`.
      kernel_regularizer: Kernel regularizer for conv layers. Defaults to None.
      interpolation: The interpolation method for upsampling. Defaults to
        `bilinear`.
      use_depthwise_convolution: Allows spatial pooling to be separable
        depthwise convolusions. [Encoder-Decoder with Atrous Separable
        Convolution for Semantic Image Segmentation](
         https://arxiv.org/pdf/1802.02611.pdf)
      **kwargs: Other keyword arguments for the layer.
    """
    super().__init__(
        output_channels=output_channels,
        dilation_rates=dilation_rates,
        use_sync_bn=use_sync_bn,
        batchnorm_momentum=batchnorm_momentum,
        batchnorm_epsilon=batchnorm_epsilon,
        activation=activation,
        dropout=dropout,
        kernel_initializer=kernel_initializer,
        kernel_regularizer=kernel_regularizer,
        interpolation=interpolation,
        pool_kernel_size=pool_kernel_size,
        use_depthwise_convolution=use_depthwise_convolution)

    self._activation_fn = tfmot.quantization.keras.QuantizeWrapperV2(
        tf_utils.get_activation(activation, use_keras_layer=True),
        configs.Default8BitActivationQuantizeConfig())
    self._activation_fn_no_quant = (
        tf_utils.get_activation(activation, use_keras_layer=True))

  def build(self, input_shape):
    height = input_shape[1]
    width = input_shape[2]
    channels = input_shape[3]

    norm_layer = (
        tf.keras.layers.experimental.SyncBatchNormalization
        if self._use_sync_bn else tf.keras.layers.BatchNormalization)
    norm_with_quantize = _quantize_wrapped_layer(
        norm_layer, configs.Default8BitOutputQuantizeConfig())
    norm = norm_with_quantize if self._activation not in [
        'relu', 'relu6'
    ] else _quantize_wrapped_layer(norm_layer, configs.NoOpQuantizeConfig())

    conv2d_quantized = _quantize_wrapped_layer(
        tf.keras.layers.Conv2D,
        configs.Default8BitConvQuantizeConfig(['kernel'], ['activation'],
                                              False))
    depthwise_conv2d_quantized_output_quantized = _quantize_wrapped_layer(
        tf.keras.layers.DepthwiseConv2D,
        configs.Default8BitConvQuantizeConfig(['depthwise_kernel'],
                                              ['activation'], True))

    self.aspp_layers = []

    conv1 = conv2d_quantized(
        filters=self._output_channels,
        kernel_size=(1, 1),
        kernel_initializer=self._kernel_initializer,
        kernel_regularizer=self._kernel_regularizer,
        use_bias=False,
        activation=NoOpActivation())
    norm1 = norm(
        axis=self._bn_axis,
        momentum=self._batchnorm_momentum,
        epsilon=self._batchnorm_epsilon)

    self.aspp_layers.append([conv1, norm1])

    for dilation_rate in self._dilation_rates:
      leading_layers = []
      kernel_size = (3, 3)
      if self._use_depthwise_convolution:
        leading_layers += [
            depthwise_conv2d_quantized_output_quantized(
                depth_multiplier=1,
                kernel_size=kernel_size,
                padding='same',
                depthwise_regularizer=self._kernel_regularizer,
                depthwise_initializer=self._kernel_initializer,
                dilation_rate=dilation_rate,
                use_bias=False,
                activation=NoOpActivation())
        ]
        kernel_size = (1, 1)
      conv_dilation = leading_layers + [
          conv2d_quantized(
              filters=self._output_channels,
              kernel_size=kernel_size,
              padding='same',
              kernel_regularizer=self._kernel_regularizer,
              kernel_initializer=self._kernel_initializer,
              dilation_rate=dilation_rate,
              use_bias=False,
              activation=NoOpActivation())
      ]
      norm_dilation = norm(
          axis=self._bn_axis,
          momentum=self._batchnorm_momentum,
          epsilon=self._batchnorm_epsilon)

      self.aspp_layers.append(conv_dilation + [norm_dilation])

    if self._pool_kernel_size is None:
      pooling = [
          _quantize_wrapped_layer(
              tf.keras.layers.GlobalAveragePooling2D,
              configs.Default8BitQuantizeConfig([], [], True))(),
          _quantize_wrapped_layer(
              tf.keras.layers.Reshape,
              configs.Default8BitQuantizeConfig([], [], True))((1, 1, channels))
      ]
    else:
      pooling = [
          _quantize_wrapped_layer(
              tf.keras.layers.AveragePooling2D,
              configs.Default8BitQuantizeConfig([], [],
                                                True))(self._pool_kernel_size)
      ]

    conv2 = conv2d_quantized(
        filters=self._output_channels,
        kernel_size=(1, 1),
        kernel_initializer=self._kernel_initializer,
        kernel_regularizer=self._kernel_regularizer,
        use_bias=False,
        activation=NoOpActivation())
    norm2 = norm(
        axis=self._bn_axis,
        momentum=self._batchnorm_momentum,
        epsilon=self._batchnorm_epsilon)

    self.aspp_layers.append(pooling + [conv2, norm2])

    resizing = _quantize_wrapped_layer(
        tf.keras.layers.Resizing, configs.Default8BitQuantizeConfig([], [],
                                                                    True))
    self._resizing_layer = resizing(
        height, width, interpolation=self._interpolation)

    self._projection = [
        conv2d_quantized(
            filters=self._output_channels,
            kernel_size=(1, 1),
            kernel_initializer=self._kernel_initializer,
            kernel_regularizer=self._kernel_regularizer,
            use_bias=False,
            activation=NoOpActivation()),
        norm_with_quantize(
            axis=self._bn_axis,
            momentum=self._batchnorm_momentum,
            epsilon=self._batchnorm_epsilon)
    ]
    self._dropout_layer = tf.keras.layers.Dropout(rate=self._dropout)
    concat = _quantize_wrapped_layer(
        tf.keras.layers.Concatenate,
        configs.Default8BitQuantizeConfig([], [], True))
    self._concat_layer = concat(axis=-1)

  def call(self,
           inputs: tf.Tensor,
           training: Optional[bool] = None) -> tf.Tensor:
    if training is None:
      training = tf.keras.backend.learning_phase()
    result = []
    for i, layers in enumerate(self.aspp_layers):
      x = inputs
      for layer in layers:
        # Apply layers sequentially.
        x = layer(x, training=training)
      x = self._activation_fn(x)

      # Apply resize layer to the end of the last set of layers.
      if i == len(self.aspp_layers) - 1:
        x = self._resizing_layer(x)

      result.append(tf.cast(x, inputs.dtype))
    x = self._concat_layer(result)
    for layer in self._projection:
      x = layer(x, training=training)
    x = self._activation_fn_no_quant(x)
    return self._dropout_layer(x)


@tf.keras.utils.register_keras_serializable(package='Vision')
class ASPPQuantized(aspp.ASPP):
  """Creates a quantized Atrous Spatial Pyramid Pooling (ASPP) layer."""

  def __init__(
      self,
      level: int,
      dilation_rates: List[int],
      num_filters: int = 256,
      pool_kernel_size: Optional[int] = None,
      use_sync_bn: bool = False,
      norm_momentum: float = 0.99,
      norm_epsilon: float = 0.001,
      activation: str = 'relu',
      dropout_rate: float = 0.0,
      kernel_initializer: str = 'VarianceScaling',
      kernel_regularizer: Optional[tf.keras.regularizers.Regularizer] = None,
      interpolation: str = 'bilinear',
      use_depthwise_convolution: bool = False,
      spp_layer_version: str = 'v1',
      output_tensor: bool = True,
      **kwargs):
    """Initializes an Atrous Spatial Pyramid Pooling (ASPP) layer.

    Args:
      level: An `int` level to apply ASPP.
      dilation_rates: A `list` of dilation rates.
      num_filters: An `int` number of output filters in ASPP.
      pool_kernel_size: A `list` of [height, width] of pooling kernel size or
        None. Pooling size is with respect to original image size, it will be
        scaled down by 2**level. If None, global average pooling is used.
      use_sync_bn: A `bool`. If True, use synchronized batch normalization.
      norm_momentum: A `float` of normalization momentum for the moving average.
      norm_epsilon: A `float` added to variance to avoid dividing by zero.
      activation: A `str` activation to be used in ASPP.
      dropout_rate: A `float` rate for dropout regularization.
      kernel_initializer: A `str` name of kernel_initializer for convolutional
        layers.
      kernel_regularizer: A `tf.keras.regularizers.Regularizer` object for
        Conv2D. Default is None.
      interpolation: A `str` of interpolation method. It should be one of
        `bilinear`, `nearest`, `bicubic`, `area`, `lanczos3`, `lanczos5`,
        `gaussian`, or `mitchellcubic`.
      use_depthwise_convolution: If True depthwise separable convolutions will
        be added to the Atrous spatial pyramid pooling.
      spp_layer_version: A `str` of spatial pyramid pooling layer version.
      output_tensor: Whether to output a single tensor or a dictionary of
        tensor. Default is true.
      **kwargs: Additional keyword arguments to be passed.
    """
    super().__init__(
        level=level,
        dilation_rates=dilation_rates,
        num_filters=num_filters,
        pool_kernel_size=pool_kernel_size,
        use_sync_bn=use_sync_bn,
        norm_momentum=norm_momentum,
        norm_epsilon=norm_epsilon,
        activation=activation,
        dropout_rate=dropout_rate,
        kernel_initializer=kernel_initializer,
        kernel_regularizer=kernel_regularizer,
        interpolation=interpolation,
        use_depthwise_convolution=use_depthwise_convolution,
        spp_layer_version=spp_layer_version,
        output_tensor=output_tensor,
        **kwargs)

    self._aspp_layer = SpatialPyramidPoolingQuantized

  def call(self, inputs: Union[tf.Tensor, Mapping[str,
                                                  tf.Tensor]]) -> tf.Tensor:
    """Calls the Atrous Spatial Pyramid Pooling (ASPP) layer on an input.

    The output of ASPP will be a dict of {`level`, `tf.Tensor`} even if only one
    level is present, if output_tensor is false. Hence, this will be compatible
    with the rest of the segmentation model interfaces.
    If output_tensor is true, a single tensot is output.

    Args:
      inputs: A `tf.Tensor` of shape [batch, height_l, width_l, filter_size] or
        a `dict` of `tf.Tensor` where
        - key: A `str` of the level of the multilevel feature maps.
        - values: A `tf.Tensor` of shape [batch, height_l, width_l,
          filter_size].

    Returns:
      A `tf.Tensor` of shape [batch, height_l, width_l, filter_size] or a `dict`
        of `tf.Tensor` where
        - key: A `str` of the level of the multilevel feature maps.
        - values: A `tf.Tensor` of output of ASPP module.
    """
    level = str(self._config_dict['level'])
    backbone_output = inputs[level] if isinstance(inputs, dict) else inputs
    return self.aspp(backbone_output)
