code: def test_function(self):
      @utils.decorator
      def double(wrapped, instance, args, kwargs):
          self.assertIsNone(instance)
          return 2 * wrapped(*args, **kwargs)
  
      f = double(
          lambda x, y: x**y
      )  # pylint: disable=no-value-for-parameter
      self.assertEqual(f(3, 4), 2 * (3**4))
  
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 DecoratorTest obj's underlying member method code with example usage: obj.test_function() and returns: unknown