code: def test_expose_node(self):
      image_shape = [3, 16, 16]
      input_shape = [2] + image_shape
      input = Input(shape=input_shape, name="input1")
  
      def l1(x):
          x1 = x.index_select(1, 0)  # input is [B, 2, 3, 16, 16]
          x2 = x.index_select(1, 0)
          return abs(x1 - x2)
  
      output = Lambda(function=l1)(input)
      model = Model(input, output)
  
      mock_data = np.random.uniform(0, 1, [10] + input_shape)
      out_data = model.forward(mock_data)
      assert out_data.shape == (10, 3, 16, 16)
  
imports: import keras.backend
  import keras.layers
  import numpy
  import pytest
  from test.zoo.pipeline.utils.test_utils import ZooTestCase
  from zoo.pipeline.api.autograd import *
  import zoo.pipeline.api.autograd
  from zoo.pipeline.api.keras.layers import *
  from zoo.pipeline.api.keras.models import Sequential, Model
  from zoo.pipeline.api.utils import remove_batch
label_desc: Use image node_id 20 for calling the TestOperator obj's underlying member method code with example usage: obj.test_expose_node() and returns: abs