class_docstr: Cache tests for bijectors that don't return new things.
code: def inverse_impl(self, struct):
      y, x = struct
      return x, y
  
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 2 for calling the IdentityCacheTest obj's underlying member method code with example usage: obj.inverse_impl(struct) and returns: x,  y