code: def layer_op(self, *args, **kwargs):
      msg = "method 'layer_op' in '{}'".format(type(self).__name__)
      tf.logging.fatal(msg)
      raise NotImplementedError
  
imports: from __future__ import absolute_import, print_function
  from abc import ABCMeta, abstractmethod
  import numpy
  import tensorflow
  from six import with_metaclass
  from niftynet.engine.application_variables import RESTORABLE
label_desc: Use image node_id 2 for calling the Layer obj's underlying member method code with example usage: obj.layer_op() without return types