text: import torch
  import torch.nn as nn
  
  OPS = {
    'none' : lambda C, stride, affine: Zero(stride),
    'avg_pool_3x3' : lambda C, stride, affine: nn.AvgPool2d(3, stride=stride, padding=1, count_include_pad=False),
    'max_pool_3x3' : lambda C, stride, affine: nn.MaxPool2d(3, stride=stride, padding=1),
    'skip_connect' : lambda C, stride, affine: Identity() if stride == 1 else FactorizedReduce(C, C, affine=affine),
    'sep_conv_3x3' : lambda C, stride, affine: SepConv(C, C, 3, stride, 1, affine=affine),
    'sep_conv_5x5' : lambda C, stride, affine: SepConv(C, C, 5, stride, 2, affine=affine),
    'sep_conv_7x7' : lambda C, stride, affine: SepConv(C, C, 7, stride, 3, affine=affine),
    'dil_conv_3x3' : lambda C, stride, affine: DilConv(C, C, 3, stride, 2, 2, affine=affine),
    'dil_conv_5x5' : lambda C, stride, affine: DilConv(C, C, 5, stride, 4, 2, affine=affine),
    'conv_7x1_1x7' : lambda C, stride, affine: nn.Sequential(
      nn.ReLU(inplace=False),
      nn.Conv2d(C, C, (1,7), stride=(1, stride), padding=(0, 3), bias=False),
      nn.Conv2d(C, C, (7,1), stride=(stride, 1), padding=(3, 0), bias=False),
      nn.BatchNorm2d(C, affine=affine)
    ),
  }
  
  class ReLUConvBN(nn.Module):
    def __init__(self, C_in, C_out, kernel_size, stride, padding, affine=True):
      super(ReLUConvBN, self).__init__()
      self.op = nn.Sequential(
        nn.ReLU(inplace=False),
        nn.Conv2d(C_in, C_out, kernel_size, stride=stride, padding=padding, bias=False),
        nn.BatchNorm2d(C_out, affine=affine)
      )
  
    def forward(self, x):
      return self.op(x)
  
  class DilConv(nn.Module):
    def __init__(self, C_in, C_out, kernel_size, stride, padding, dilation, affine=True):
      super(DilConv, self).__init__()
      self.op = nn.Sequential(
        nn.ReLU(inplace=False),
        nn.Conv2d(C_in, C_in, kernel_size=kernel_size, stride=stride, padding=padding, dilation=dilation, groups=C_in, bias=False),
        nn.Conv2d(C_in, C_out, kernel_size=1, padding=0, bias=False),
        nn.BatchNorm2d(C_out, affine=affine),
      )
  
    def forward(self, x):
      return self.op(x)
  
  class SepConv(nn.Module):
    def __init__(self, C_in, C_out, kernel_size, stride, padding, affine=True):
      super(SepConv, self).__init__()
      self.op = nn.Sequential(
        nn.ReLU(inplace=False),
        nn.Conv2d(C_in, C_in, kernel_size=kernel_size, stride=stride, padding=padding, groups=C_in, bias=False),
        nn.Conv2d(C_in, C_in, kernel_size=1, padding=0, bias=False),
        nn.BatchNorm2d(C_in, affine=affine),
        nn.ReLU(inplace=False),
        nn.Conv2d(C_in, C_in, kernel_size=kernel_size, stride=1, padding=padding, groups=C_in, bias=False),
        nn.Conv2d(C_in, C_out, kernel_size=1, padding=0, bias=False),
        nn.BatchNorm2d(C_out, affine=affine),
      )
  
    def forward(self, x):
      return self.op(x)
  
  class Identity(nn.Module):
    def __init__(self):
      super(Identity, self).__init__()
  
    def forward(self, x):
      return x
  
  class Zero(nn.Module):
    def __init__(self, stride):
      super(Zero, self).__init__()
      self.stride = stride
  
    def forward(self, x):
      if self.stride == 1:
        return x.mul(0.)
      return x[:,:,::self.stride,::self.stride].mul(0.)
  
  class FactorizedReduce(nn.Module):
    def __init__(self, C_in, C_out, affine=True):
      super(FactorizedReduce, self).__init__()
      assert C_out % 2 == 0
      self.relu = nn.ReLU(inplace=False)
      self.conv_1 = nn.Conv2d(C_in, C_out // 2, 1, stride=2, padding=0, bias=False)
      self.conv_2 = nn.Conv2d(C_in, C_out // 2, 1, stride=2, padding=0, bias=False)  # ouput channel이 절반이 되는 것 
      self.bn = nn.BatchNorm2d(C_out, affine=affine)
  
    def forward(self, x):
      x = self.relu(x)
      out = torch.cat([self.conv_1(x), self.conv_2(x[:,:,1:,1:])], dim=1)
      out = self.bn(out)
      return out