class_docstr: Most of ImageNet pretrained models are inherited from this class
  so that it provides some common interfaces.
code: def _input_shape(self):
      raise NotImplementedError("input size is not implemented")
  
file_path: nnabla/python/src/nnabla/models/imagenet/base.py
imports: from __future__ import absolute_import
  import nnabla
  from nnabla.utils.nnp_graph import NnpLoader
  from ..utils import *
label_desc: Use image node_id 3 for calling the ImageNetBase obj's underlying member method code with example usage: obj._input_shape() without return types