def arrival_time(self, x_image, y_image, kwargs_lens):
        """

        :param x_image: image position
        :param y_image: image position
        :param kwargs_lens: lens model parameter keyword argument list
        :return:
        """
        if hasattr(self.lens_model, 'arrival_time'):
            arrival_time = self.lens_model.arrival_time(x_image, y_image, kwargs_lens)
        else:
            x_source, y_source = self.lens_model.ray_shooting(x_image, y_image, kwargs_lens)
            fermat_pot = self.lens_model.fermat_potential(x_image, y_image, x_source, y_source, kwargs_lens)
            if not hasattr(self, '_lensCosmo'):
                raise ValueError("LensModel class was not initalized with lens and source redshifts!")
            arrival_time = self._lensCosmo.time_delay_units(fermat_pot)
        return arrival_time
def arrival_time ( self , x_image , y_image , kwargs_lens ) : if hasattr ( self . lens_model , 'arrival_time' ) : arrival_time = self . lens_model . arrival_time ( x_image , y_image , kwargs_lens ) else : x_source , y_source = self . lens_model . ray_shooting ( x_image , y_image , kwargs_lens ) fermat_pot = self . lens_model . fermat_potential ( x_image , y_image , x_source , y_source , kwargs_lens ) if not hasattr ( self , '_lensCosmo' ) : raise ValueError ( "LensModel class was not initalized with lens and source redshifts!" ) arrival_time = self . _lensCosmo . time_delay_units ( fermat_pot ) return arrival_time
:param x_image: image position
        :param y_image: image position
        :param kwargs_lens: lens model parameter keyword argument list
        :return: