class_docstr: Tests for tf2_utils.create_variables method.
code: def test_none_output(self):
      model = tf2_utils.to_sonnet_module(lambda x: None)
      input_spec = specs.Array(shape=(10,), dtype=np.float32)
      expected_spec = None
      output_spec = tf2_utils.create_variables(model, [input_spec])
      self.assertEqual(model.variables, ())
      self.assertEqual(output_spec, expected_spec)
  
imports: from typing import Sequence, Tuple
  from acme import specs
  from acme.tf import utils
  import numpy
  import sonnet
  import tensorflow
  from absl.testing import absltest
  from absl.testing import parameterized
label_desc: Use image node_id 5 for calling the CreateVariableTest obj's underlying member method code with example usage: obj.test_none_output() without return types