class_docstr: The layers require a randomisation process, to randomly
  change some of the layer's states on the fly.
code: def randomise(self, *args, **kwargs):
      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 RandomisedLayer obj's underlying member method code with example usage: obj.randomise() without return types