Borrow the main body of the tf api compat test for diffing and api generation. The py_object_to_proto lib need a slight update to config the root path since we will make tensorflow.keras as the root when visiting all the keras related API. PiperOrigin-RevId: 360954528 Change-Id: I1c0d6e3310479cc7cf66ffd1f8b1a060f7f5029b