code: def _get_method(self, prefix, gpu):
      suffix = "gpu" if gpu else "cpu"
      return getattr(self.f, prefix + "_" + suffix)
  
imports: import unittest
  import mock
  import numpy
  import six
  import chainer
  from chainer import _backprop_utils
  from chainer.backends import cuda
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 1 for calling the TestFunctionNode obj's underlying member method code with example usage: obj._get_method(prefix, gpu) and returns: getattr