Defines a matplotlib annulus path from two patches.

        This preserves the cubic Bezier curves (CURVE4) of the aperture
        paths.

        # This is borrowed from photutils aperture.

def _make_annulus_path(patch_inner, patch_outer):
        """
        Defines a matplotlib annulus path from two patches.

        This preserves the cubic Bezier curves (CURVE4) of the aperture
        paths.

        # This is borrowed from photutils aperture.
        """

        import matplotlib.path as mpath

        path_inner = patch_inner.get_path()
        transform_inner = patch_inner.get_transform()
        path_inner = transform_inner.transform_path(path_inner)

        path_outer = patch_outer.get_path()
        transform_outer = patch_outer.get_transform()
        path_outer = transform_outer.transform_path(path_outer)

        verts_inner = path_inner.vertices[:-1][::-1]
        verts_inner = np.concatenate((verts_inner, [verts_inner[-1]]))

        verts = np.vstack((path_outer.vertices, verts_inner))
        codes = np.hstack((path_outer.codes, path_inner.codes))

        return mpath.Path(verts, codes)