code: def test_invalid_strings(self, data_format):
      with self.assertRaisesRegex(
          ValueError,
          "Unable to extract channel information from '{}'.".format(
              data_format
          ),
      ):
          utils.get_channel_index(data_format)
  
imports: from absl.testing import parameterized
  import numpy
  from sonnet.src import initializers
  from sonnet.src import test_utils
  from sonnet.src import utils
  import tensorflow
label_desc: Use image node_id 3 for calling the ChannelIndexTest obj's underlying member method code with example usage: obj.test_invalid_strings(data_format) without return types