code: def test_loop(self):
      def body(lop):
          return (AutoDiag(lop.matvec(tf.ones([3]) * 2.0)),)
  
      init_lop = AutoDiag(tf.ones([3]))
      (lop,) = tf.while_loop(
          cond=lambda _: True,
          body=body,
          loop_vars=(init_lop,),
          maximum_iterations=3,
      )
      self.assertAllClose(
          2.0**3 * tf.ones([3]), lop.matvec(tf.ones([3]))
      )
  
imports: import functools
  import os
  from absl import flags
  from absl.testing import parameterized
  import tensorflow.compat.v2
  from tensorflow_probability.python.bijectors import bijector
  from tensorflow_probability.python.bijectors import reshape
  from tensorflow_probability.python.bijectors import scale
  from tensorflow_probability.python.bijectors import shift
  from tensorflow_probability.python.bijectors import transform_diagonal
  from tensorflow_probability.python.distributions import independent
  from tensorflow_probability.python.distributions import normal
  from tensorflow_probability.python.distributions import transformed_distribution
  from tensorflow_probability.python.experimental.distributions import mvn_precision_factor_linop
  from tensorflow_probability.python.internal import auto_composite_tensor
  from tensorflow_probability.python.internal import tensor_util
  from tensorflow_probability.python.internal import test_util
  from absl.testing import absltest
label_desc: Use image node_id 3 for calling the AutoCompositeTensorTest obj's underlying member method code with example usage: obj.test_loop() and returns: AutoDiag