code: def hybrid_forward(self, F, x, *args, **kwargs):
      raise NotImplementedError
  
file_path: gluonts/test/mx/test_mx_serde.py
imports: from typing import List
  import pytest
  import mxnet
  import numpy
  from gluonts.core import serde
  from gluonts.core.component import equals
  from gluonts.pydantic import BaseModel
label_desc: Use image node_id 2 for calling the MyGluonBlock obj's underlying member method code with example usage: obj.hybrid_forward(F, x) without return types