code: def testGradientThroughParams(self):
      loc = tf.Variable([-5.0, 0.0, 5.0])
      scale = tf.Variable(2.0)
      d = laplace.Laplace(loc=loc, scale=scale, validate_args=True)
      with tf.GradientTape() as tape:
          loss = -d.log_prob([1.0, 2.0, 3.0])
      grad = tape.gradient(loss, d.trainable_variables)
      self.assertLen(grad, 2)
      self.assertAllNotNone(grad)
  
imports: import numpy
  from scipy import stats
  import tensorflow.compat.v2
  from tensorflow_probability.python.distributions import kullback_leibler
  from tensorflow_probability.python.distributions import laplace
  from tensorflow_probability.python.internal import samplers
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.math import gradient
label_desc: Use image node_id 22 for calling the LaplaceTest obj's underlying member method code with example usage: obj.testGradientThroughParams() without return types