OK, it's good that you are removing the time from here. @srjoglekar246 can add a check in his ```MovingRefFrame``` if desired. To be clear though, just taking the derivative in the global frame isn't a good solution. In this case, if would not have allowed more than 1 successive rotation, raising an error on the next one.
In other cases, the users should be forced to explicitly state which frame the derivative is being taken in.