Args:
            xyz_string: string of the form 'x, y, z, +1', '-x, -y, z, -1',
                '-2y+1/2, 3x+1/2, z-y+1/2, +1', etc.
        Returns:
            MagSymmOp object

def from_xyzt_string(xyzt_string):
        """
        Args:
            xyz_string: string of the form 'x, y, z, +1', '-x, -y, z, -1',
                '-2y+1/2, 3x+1/2, z-y+1/2, +1', etc.
        Returns:
            MagSymmOp object
        """
        symmop = SymmOp.from_xyz_string(xyzt_string.rsplit(',', 1)[0])
        try:
            time_reversal = int(xyzt_string.rsplit(',', 1)[1])
        except:
            raise Exception("Time reversal operator could not be parsed.")
        return MagSymmOp.from_symmop(symmop, time_reversal)