class_docstr: Residual block with skip connection.
code: def forward(self, x):
      if hasattr(self, "skip"):
          x = self.skip(x) + self.residual(x)
      else:
          x = x + self.residual(x)
      x = self.relu(x)
      return x
  
imports: import torch.nn
  from .r2plus1_util import r2plus1_unit
label_desc: Use image node_id 2 for calling the ResBlock obj's underlying member method code with example usage: obj.forward(x) and returns: x