code: def _pair(x):
      if isinstance(x, chainer.utils.collections_abc.Iterable):
          return x
      return x, x
  
imports: import unittest
  import numpy
  import chainer
  from chainer import cuda
  from chainer import functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
  from chainer.testing import condition
  from chainer_tests.functions_tests.pooling_tests import pooling_nd_helper
label_desc: Use image node_id 1 for calling a global function with example usage: _pair(x) and returns: x,  x, x