I think isinstance( retval, (tuple, list)) is wrong as returned value will be an instance of (array, list) or (dict, list) etc.
In my case, my environment return array and dict info upon reset. Here this code doesn't interpret this as having info and because it is a tuple of array, list and not tuple of tuple,list

Suggested edit
reset_returns_info = isinstance( retval[0], np.ndarray) and len(retval) == 2 and isinstance( retval[1], list)