code: def test_deepvariant_channel_names(self, num_channels):
      output = vis._deepvariant_channel_names(num_channels)
      self.assertLen(output, num_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 19 for calling the VisTest obj's underlying member method code with example usage: obj.test_deepvariant_channel_names(num_channels) without return types