code: def forward(self, x, mid_fea):
      x = self.layer1(x)  # N x 256 x 32 x 32
      print(x.shape)
      x = self.layer2(x)  # N x 128 x 64 x 64
      print(x.shape)
      x = self.layer3(x)  # N x 64 x 128 x 128
      print(x.shape)
      x = self.layer4(x)  # N x 32 x 256 x 256
      print(x.shape)
      x = self.conv1(x)
      x = self.bn1(x)
      x = self.leaky_relu(x)
      x = self.conv2(x)
  
      alpha = (self.tanh(x) + 1.0) / 2.0
  
      return alpha
  
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddleseg.models import layers
  from paddleseg import utils
  from paddleseg.cvlibs import manager, param_init
  from ppmatting.models.layers import GuidedCxtAtten
label_desc: Use image node_id 3 for calling the ResNet_D_Dec obj's underlying member method code with example usage: obj.forward(x, mid_fea) and returns: alpha