class_docstr: Cache tests for bijectors that don't return new things.
code: def test_arg(self):
      return tf.constant(1.0), tf.constant(2.0)
  
imports: from absl.testing import parameterized
  import tensorflow.compat.v2
  from tensorflow_probability.python.internal import cache_util
  from tensorflow_probability.python.internal import test_util
label_desc: Use image node_id 3 for calling the IdentityCacheTest obj's underlying member method code with example usage: obj.test_arg() and returns: tf,  tf