code: def __call__(self, _order, _):
      order = numpy.arange(len(_order) - self.n_call)
      self.n_call += 1
      return order
  
imports: from __future__ import division
  import copy
  import unittest
  import numpy
  import six
  from chainer import iterators
  from chainer import serializers
  from chainer import testing
label_desc: Use image node_id 2 for calling the InvalidOrderSampler obj's underlying member method code with example usage: obj.__call__(_order, _) and returns: order