code: def shortcut(input, ch_in, ch_out, stride):
      if ch_in != ch_out:
          return conv_bn_layer(input, ch_out, 1, stride, 0, None)
      else:
          return input
  
imports: from __future__ import division
  from builtins import range
  from builtins import object
  from past.utils import old_div
  import paddle.fluid
  import math
label_desc: Use image node_id 2 for calling a global function with example usage: shortcut(input, ch_in, ch_out, stride) and returns: conv_bn_layer, input