text: """Pytorch impl of Gluon Xception
  This is a port of the Gluon Xception code and weights, itself ported from a PyTorch DeepLab impl.
  
  Gluon model: (https://gluon-cv.mxnet.io/_modules/gluoncv/model_zoo/xception.html)
  Original PyTorch DeepLab impl: https://github.com/jfzhang95/pytorch-deeplab-xception
  
  Hacked together by / Copyright 2020 Ross Wightman
  """
  from collections import OrderedDict
  
  import torch.nn as nn
  import torch.nn.functional as F
  
  from timm.data import IMAGENET_DEFAULT_MEAN, IMAGENET_DEFAULT_STD
  from ..utils.helpers import build_model_with_cfg
  from ..utils.layers import create_classifier, get_padding
  from .registry import register_model
  
  __all__ = ['Xception65']
  
  default_cfgs = {
      'gluon_xception65': {
          'url': 'https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-weights/gluon_xception-7015a15c.pth',
          'input_size': (3, 299, 299),
          'crop_pct': 0.903,
          'pool_size': (10, 10),
          'interpolation': 'bicubic',
          'mean': IMAGENET_DEFAULT_MEAN,
          'std': IMAGENET_DEFAULT_STD,
          'num_classes': 1000,
          'first_conv': 'conv1',
          'classifier': 'fc'
          # The resize parameter of the validation transform should be 333, and make sure to center crop at 299x299
      },
  }
  
  """ PADDING NOTES
  The original PyTorch and Gluon impl of these models dutifully reproduced the 
  aligned padding added to Tensorflow models for Deeplab. This padding was compensating
  for  Tensorflow 'SAME' padding. PyTorch symmetric padding behaves the way we'd want it to. 
  """
  
  
  class SeparableConv2d(nn.Module):
      def __init__(self, inplanes, planes, kernel_size=3, stride=1,
                   dilation=1, bias=False, norm_layer=None, norm_kwargs=None):
          super(SeparableConv2d, self).__init__()
          norm_kwargs = norm_kwargs if norm_kwargs is not None else {}
          self.kernel_size = kernel_size
          self.dilation = dilation
  
          # depthwise convolution
          padding = get_padding(kernel_size, stride, dilation)
          self.conv_dw = nn.Conv2d(
              inplanes, inplanes, kernel_size, stride=stride,
              padding=padding, dilation=dilation, groups=inplanes, bias=bias)
          self.bn = norm_layer(num_features=inplanes, **norm_kwargs)
          # pointwise convolution
          self.conv_pw = nn.Conv2d(inplanes, planes, kernel_size=1, bias=bias)
  
      def forward(self, x):
          x = self.conv_dw(x)
          x = self.bn(x)
          x = self.conv_pw(x)
          return x
  
  
  class Block(nn.Module):
      def __init__(self, inplanes, planes, stride=1, dilation=1, start_with_relu=True,
                   norm_layer=None, norm_kwargs=None, ):
          super(Block, self).__init__()
          norm_kwargs = norm_kwargs if norm_kwargs is not None else {}
          if isinstance(planes, (list, tuple)):
              assert len(planes) == 3
          else:
              planes = (planes,) * 3
          outplanes = planes[-1]
  
          if outplanes != inplanes or stride != 1:
              self.skip = nn.Sequential()
              self.skip.add_module('conv1', nn.Conv2d(
                  inplanes, outplanes, 1, stride=stride, bias=False)),
              self.skip.add_module('bn1', norm_layer(num_features=outplanes, **norm_kwargs))
          else:
              self.skip = None
  
          rep = OrderedDict()
          for i in range(3):
              rep['act%d' % (i + 1)] = nn.ReLU(inplace=True)
              rep['conv%d' % (i + 1)] = SeparableConv2d(
                  inplanes, planes[i], 3, stride=stride if i == 2 else 1, dilation=dilation,
                  norm_layer=norm_layer, norm_kwargs=norm_kwargs)
              rep['bn%d' % (i + 1)] = norm_layer(planes[i], **norm_kwargs)
              inplanes = planes[i]
  
          if not start_with_relu:
              del rep['act1']
          else:
              rep['act1'] = nn.ReLU(inplace=False)
          self.rep = nn.Sequential(rep)
  
      def forward(self, x):
          skip = x
          if self.skip is not None:
              skip = self.skip(skip)
          x = self.rep(x) + skip
          return x
  
  
  class Xception65(nn.Module):
      """Modified Aligned Xception.
  
      NOTE: only the 65 layer version is included here, the 71 layer variant
      was not correct and had no pretrained weights
      """
  
      def __init__(self, num_classes=1000, in_chans=3, output_stride=32, norm_layer=nn.BatchNorm2d,
                   norm_kwargs=None, drop_rate=0., global_pool='avg'):
          super(Xception65, self).__init__()
          self.num_classes = num_classes
          self.drop_rate = drop_rate
          norm_kwargs = norm_kwargs if norm_kwargs is not None else {}
          if output_stride == 32:
              entry_block3_stride = 2
              exit_block20_stride = 2
              middle_block_dilation = 1
              exit_block_dilations = (1, 1)
          elif output_stride == 16:
              entry_block3_stride = 2
              exit_block20_stride = 1
              middle_block_dilation = 1
              exit_block_dilations = (1, 2)
          elif output_stride == 8:
              entry_block3_stride = 1
              exit_block20_stride = 1
              middle_block_dilation = 2
              exit_block_dilations = (2, 4)
          else:
              raise NotImplementedError
  
          # Entry flow
          self.conv1 = nn.Conv2d(in_chans, 32, kernel_size=3, stride=2, padding=1, bias=False)
          self.bn1 = norm_layer(num_features=32, **norm_kwargs)
          self.act1 = nn.ReLU(inplace=True)
  
          self.conv2 = nn.Conv2d(32, 64, kernel_size=3, stride=1, padding=1, bias=False)
          self.bn2 = norm_layer(num_features=64)
          self.act2 = nn.ReLU(inplace=True)
  
          self.block1 = Block(
              64, 128, stride=2, start_with_relu=False, norm_layer=norm_layer, norm_kwargs=norm_kwargs)
          self.block1_act = nn.ReLU(inplace=True)
          self.block2 = Block(
              128, 256, stride=2, start_with_relu=False, norm_layer=norm_layer, norm_kwargs=norm_kwargs)
          self.block3 = Block(
              256, 728, stride=entry_block3_stride, norm_layer=norm_layer, norm_kwargs=norm_kwargs)
  
          # Middle flow
          self.mid = nn.Sequential(OrderedDict([('block%d' % i, Block(
              728, 728, stride=1, dilation=middle_block_dilation,
              norm_layer=norm_layer, norm_kwargs=norm_kwargs)) for i in range(4, 20)]))
  
          # Exit flow
          self.block20 = Block(
              728, (728, 1024, 1024), stride=exit_block20_stride, dilation=exit_block_dilations[0],
              norm_layer=norm_layer, norm_kwargs=norm_kwargs)
          self.block20_act = nn.ReLU(inplace=True)
  
          self.conv3 = SeparableConv2d(
              1024, 1536, 3, stride=1, dilation=exit_block_dilations[1],
              norm_layer=norm_layer, norm_kwargs=norm_kwargs)
          self.bn3 = norm_layer(num_features=1536, **norm_kwargs)
          self.act3 = nn.ReLU(inplace=True)
  
          self.conv4 = SeparableConv2d(
              1536, 1536, 3, stride=1, dilation=exit_block_dilations[1],
              norm_layer=norm_layer, norm_kwargs=norm_kwargs)
          self.bn4 = norm_layer(num_features=1536, **norm_kwargs)
          self.act4 = nn.ReLU(inplace=True)
  
          self.num_features = 2048
          self.conv5 = SeparableConv2d(
              1536, self.num_features, 3, stride=1, dilation=exit_block_dilations[1],
              norm_layer=norm_layer, norm_kwargs=norm_kwargs)
          self.bn5 = norm_layer(num_features=self.num_features, **norm_kwargs)
          self.act5 = nn.ReLU(inplace=True)
          self.feature_info = [
              dict(num_chs=64, reduction=2, module='act2'),
              dict(num_chs=128, reduction=4, module='block1_act'),
              dict(num_chs=256, reduction=8, module='block3.rep.act1'),
              dict(num_chs=728, reduction=16, module='block20.rep.act1'),
              dict(num_chs=2048, reduction=32, module='act5'),
          ]
  
          self.global_pool, self.fc = create_classifier(self.num_features, self.num_classes, pool_type=global_pool)
  
      def get_classifier(self):
          return self.fc
  
      def reset_classifier(self, num_classes, global_pool='avg'):
          self.num_classes = num_classes
          self.global_pool, self.fc = create_classifier(self.num_features, self.num_classes, pool_type=global_pool)
  
      def forward_features(self, x):
          # Entry flow
          x = self.conv1(x)
          x = self.bn1(x)
          x = self.act1(x)
  
          x = self.conv2(x)
          x = self.bn2(x)
          x = self.act2(x)
  
          x = self.block1(x)
          x = self.block1_act(x)
          # c1 = x
          x = self.block2(x)
          # c2 = x
          x = self.block3(x)
  
          # Middle flow
          x = self.mid(x)
          # c3 = x
  
          # Exit flow
          x = self.block20(x)
          x = self.block20_act(x)
          x = self.conv3(x)
          x = self.bn3(x)
          x = self.act3(x)
  
          x = self.conv4(x)
          x = self.bn4(x)
          x = self.act4(x)
  
          x = self.conv5(x)
          x = self.bn5(x)
          x = self.act5(x)
          return x
  
      def forward(self, x):
          x = self.forward_features(x)
          x = self.global_pool(x)
          if self.drop_rate:
              F.dropout(x, self.drop_rate, training=self.training)
          x = self.fc(x)
          return x
  
  
  def _create_gluon_xception(variant, pretrained=False, **kwargs):
      return build_model_with_cfg(
          Xception65, variant, pretrained, default_cfg=default_cfgs[variant],
          feature_cfg=dict(feature_cls='hook'), **kwargs)
  
  
  @register_model
  def gluon_xception65(pretrained=False, **kwargs):
      """ Modified Aligned Xception-65
      """
      return _create_gluon_xception('gluon_xception65', pretrained, **kwargs)
  