class_docstr: Error: model function not implement
code: def __str__(self):
      return "Function {}() is not implemented in model {}".format(
          self.function, self.model
      )
  
imports: import os
  import logging
  import paddle.fluid
label_desc: Use image node_id 2 for calling the NotImplementError obj's underlying member method code with example usage: obj.__str__() and returns: str