code: def test_analyze_diff_and_nearby_variants_and_describe_diff(
      self,
      test_case,
      expected_description,
      expected_diff_fraction,
      expected_nearby_variants,
  ):
      shape = (15, 8)
      diff_channel = np.zeros(shape) + 100
      if test_case == "nearby_variants":
          # Five columns with homozygous variants:
          diff_channel[5:, [0, 1, 2, 4, 6]] = 254
      elif test_case == "few_diffs":
          # Less than five columns with homozygous variants:
          diff_channel[5:, [2, 5]] = 254
      elif test_case == "many_diffs":
          # One read full of differences:
          diff_channel[5, 0:8] = 254
      elif test_case == "empty":
          # No reads:
          diff_channel = np.zeros(shape)
      else:
          raise ValueError("test_case not recognized")
      filler_channels = [0] * 5
      channels = filler_channels + [diff_channel]
      (
          diff_fraction,
          nearby_variants,
      ) = vis.analyze_diff_and_nearby_variants(channels)
      self.assertEqual(diff_fraction, expected_diff_fraction)
      self.assertEqual(nearby_variants, expected_nearby_variants)
      self.assertEqual(
          expected_description, vis.describe_diff(channels)
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import glob
  import os
  from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from third_party.nucleus.protos import variants_pb2
  from third_party.nucleus.testing import test_utils
  from third_party.nucleus.util import vis
  from tensorflow.core.example import example_pb2
  from tensorflow.core.example import feature_pb2
label_desc: Use image node_id 26 for calling the VisTest obj's underlying member method code with example usage: obj.test_analyze_diff_and_nearby_variants_and_describe_diff(test_case, expected_description, expected_diff_fraction, expected_nearby_variants) without return types