code: def __next__(self):
      return next(self.iterator)
  
imports: import unittest
  import numpy
  import chainer
  from chainer import backend
  from chainer.backends import _cpu
  from chainer import dataset
  from chainer import iterators
  from chainer import testing
  from chainer.training import extensions
label_desc: Use image node_id 3 for calling the DummyIterator obj's underlying member method code with example usage: obj.__next__() and returns: next