class_docstr: Test for niftynet.layer.subpixel.SubPixelLayer.
  Mostly adapted from convolution_test.py
code: def test_3d_default(self):
      data = self.get_3d_input()
  
      output_shape = self._make_output_shape(data, 2)
  
      self._test_subpixel_output_shape(data, {}, output_shape)
  
file_path: NiftyNet/tests/subpixel_test.py
imports: from __future__ import division, absolute_import, print_function
  import functools
  import numpy
  import tensorflow
  from niftynet.layer.subpixel import SubPixelLayer
  from tests.niftynet_testcase import NiftyNetTestCase
label_desc: Use image node_id 5 for calling the SubPixelTest obj's underlying member method code with example usage: obj.test_3d_default() without return types