code: def test_clip_weights_none(self):
      self.assertIsNone(
          clip_grads.compute_clip_weights(None, tf.ones(3))
      )
  
imports: from collections.abc import Mapping, Sequence
  from typing import Any, Optional
  from absl.testing import parameterized
  import tensorflow
  from tensorflow_privacy.privacy.fast_gradient_clipping import clip_grads
  from tensorflow_privacy.privacy.fast_gradient_clipping import common_test_utils
  from tensorflow_privacy.privacy.fast_gradient_clipping import layer_registry
  from tensorflow_privacy.privacy.fast_gradient_clipping import type_aliases
label_desc: Use image node_id 2 for calling the DirectWeightsTest obj's underlying member method code with example usage: obj.test_clip_weights_none() without return types