code: def testVariableGradients(self):
      map_values = tf.Variable([0.3, 0.5])
      b = categorical_to_discrete.CategoricalToDiscrete(
          map_values=map_values, validate_args=True
      )
      with tf.GradientTape() as tape:
          y = tf.reduce_sum(b.forward([0, 1]))
      grads = tape.gradient(y, [map_values])
      self.assertAllNotNone(grads)
  
imports: import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.bijectors import bijector_test_util
  from tensorflow_probability.python.bijectors import categorical_to_discrete
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.math import gradient
label_desc: Use image node_id 11 for calling the CategoricalToDiscreteTest obj's underlying member method code with example usage: obj.testVariableGradients() without return types