code: def test_length_diff_generator_key_with_required(self):
      path1 = types.FeaturePath(["f1"])
      path2 = types.FeaturePath(["f2"])
      required_path = types.FeaturePath(["required"])
      required_paths = [path1, path2, required_path]
      generator = length_diff_generator.LengthDiffGenerator(
          path1, path2, required_paths
      )
      expected_key = (
          "LengthDiffGenerator",
          path1,
          path2,
          path1,
          path2,
          required_path,
      )
      self.assertDictEqual(
          {expected_key: None}, {generator.get_key(): None}
      )
      self.assertDictEqual(
          {expected_key: None},
          {
              length_diff_generator.LengthDiffGenerator.key(
                  path1, path2, required_paths
              ): None
          },
      )
  
file_path: data-validation/tensorflow_data_validation/statistics/generators/constituents/length_diff_generator_test.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import absltest
  import pyarrow
  from tensorflow_data_validation import types
  from tensorflow_data_validation.statistics.generators import input_batch
  from tensorflow_data_validation.statistics.generators.constituents import length_diff_generator
label_desc: Use image node_id 2 for calling the LengthDiffGeneratorTest obj's underlying member method code with example usage: obj.test_length_diff_generator_key_with_required() without return types