Change the ellipsoid used in the calculation.

def set_ellipsoid(self, ellipsoid):
        """
        Change the ellipsoid used in the calculation.
        """
        if not isinstance(ellipsoid, (list, tuple)):
            try:
                self.ELLIPSOID = ELLIPSOIDS[ellipsoid]
                self.ellipsoid_key = ellipsoid
            except KeyError:
                raise Exception(
                    "Invalid ellipsoid. See geopy.distance.ELIPSOIDS"
                )
        else:
            self.ELLIPSOID = ellipsoid
            self.ellipsoid_key = None
        return