message: Don't use magic string for API symbol "tensorflow".
diff: @@ -470,7 +470,8 @@ def register_dispatchers():
  _BINARY_ELEMENTWISE_OPS + [x[0] for x in _RAGGED_DISPATCH_OPS])
  for op in op_list:
  _, undecorated_op = tf_decorator.unwrap(op)
  - if not hasattr(undecorated_op, tf_export.API_ATTRS['tensorflow'].names):
  + if not hasattr(undecorated_op,
  + tf_export.API_ATTRS[tf_export.TENSORFLOW_API_NAME].names):
  raise AssertionError('Expected %s to be an exported symbol '
  '(while adding a RaggedTensor dispatcher)')
  