class_docstr: Tests clip_and_aggreate_gradients.
code: def _to_dense_array(self, g):
      if g is None:
          return None
      return np.array(tf.convert_to_tensor(g))
  
file_path: privacy/tensorflow_privacy/privacy/optimizers/clip_and_aggregate_gradients_test.py
imports: from absl.testing import parameterized
  import numpy
  import tensorflow
  from tensorflow_privacy.privacy.optimizers import clip_and_aggregate_gradients
label_desc: Use image node_id 3 for calling the ClipAndAggregateGradientsTest obj's underlying member method code with example usage: obj._to_dense_array(g) and returns: np, None