def potential_from_grid(self, grid):
        """
        Calculate the potential at a given set of arc-second gridded coordinates.

        Parameters
        ----------
        grid : grids.RegularGrid
            The grid of (y,x) arc-second coordinates the deflection angles are computed on.
        """
        eta = self.grid_to_elliptical_radii(grid)
        return 2.0 * self.einstein_radius_rescaled * eta
Calculate the potential at a given set of arc-second gridded coordinates.

        Parameters
        ----------
        grid : grids.RegularGrid
            The grid of (y,x) arc-second coordinates the deflection angles are computed on.