code: def get_3d_input(self):
      input_shape = (16, 16, 16)
      x = np.random.randint(-10, 10, size=input_shape)
      return x
  
file_path: NiftyNet/tests/mean_variance_normalisation_test.py
imports: from __future__ import absolute_import, print_function
  import numpy
  import tensorflow
  from niftynet.layer.binary_masking import BinaryMaskingLayer
  from niftynet.layer.mean_variance_normalisation import MeanVarNormalisationLayer
  from tests.niftynet_testcase import NiftyNetTestCase
label_desc: Use image node_id 1 for calling the BinaryMaskingTEst obj's underlying member method code with example usage: obj.get_3d_input() and returns: x