class_docstr: PrePostProcessLayer
class_docstr_tok: ["PrePostProcessLayer"]
code: def forward(self, x, residual=None):
      for i, cmd in enumerate(self.process_cmd):
          if cmd == "a":
              x = self.functors[i](x, residual)
          else:
              x = self.functors[i](x)
      return x
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import math
  import paddle
  from paddle import ParamAttr, nn
  from paddle import nn, ParamAttr
  from paddle.nn import functional
  import numpy
label_desc: Use image node_id 2 for calling the PrePostProcessLayer obj's underlying member method code with example usage: obj.forward(x, residual) and returns: x