message: restore a remove export
diff: @@ -39,6 +39,8 @@ from tensorflow.python.util import deprecation
  from tensorflow.python.util import nest
  from tensorflow.python.util.tf_export import tf_export
  +
  +@tf_export(v1=["map_fn"])
  @deprecation.deprecated_args(None, "Use fn_output_signature instead", "dtype")
  def map_fn(fn,
  elems,
  