code: def test_returns_index_channels_last(self, data_format):
      self.assertEqual(utils.get_channel_index(data_format), -1)
  
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 2 for calling the ChannelIndexTest obj's underlying member method code with example usage: obj.test_returns_index_channels_last(data_format) without return types