docstr: get model optimizer
docstr_tok: ["get","model","optimizer"]
code: def optimizer(self):
      "get model optimizer"
      raise NotImplementError(self, self.optimizer)
  
imports: import os
  import logging
  import paddle.fluid
label_desc: Use image node_id 4 for calling the ModelBase obj's underlying member method code with example usage: obj.optimizer() without return types