How to use the healpy.nest2ring function in healpy

# number of subpixels in each superpixel
    npix = np.array((nside_subpix // nside_superpix) ** 2, ndmin=1)
    x = np.arange(np.max(npix), dtype=int)
    idx = idx * npix

    if not np.all(npix[0] == npix):
        x = np.broadcast_to(x, idx.shape + x.shape)
        idx = idx[..., None] + x
        idx[x >= np.broadcast_to(npix[..., None], x.shape)] = INVALID_INDEX.int
    else:
        idx = idx[..., None] + x

    if not nest:
        m = idx == INVALID_INDEX.int
        idx[m] = 0
        idx = hp.nest2ring(nside_subpix[..., None], idx)
        idx[m] = INVALID_INDEX.int

    return idx

"""
        import healpy as hp
        tokens = re.split('\(|\)|,', region)
        if tokens[0] == 'DISK':
            vec = coords_to_vec(float(tokens[1]), float(tokens[2]))
            ilist = hp.query_disc(nside, vec[0], np.radians(float(tokens[3])),
                                  inclusive=False, nest=nest)
        elif tokens[0] == 'DISK_INC':
            vec = coords_to_vec(float(tokens[1]), float(tokens[2]))
            ilist = hp.query_disc(nside, vec[0], np.radians(float(tokens[3])),
                                  inclusive=True, fact=int(tokens[4]),
                                  nest=nest)
        elif tokens[0] == 'HPX_PIXEL':
            nside_pix = int(tokens[2])
            if tokens[1] == 'NESTED':
                ipix_ring = hp.nest2ring(nside_pix, int(tokens[3]))
            elif tokens[1] == 'RING':
                ipix_ring = int(tokens[3])
            else:
                raise Exception(
                    "Did not recognize ordering scheme %s" % tokens[1])
            ilist = match_hpx_pixel(nside, nest, nside_pix, ipix_ring)
        else:
            raise Exception(
                "HPX.get_index_list did not recognize region type %s" % tokens[0])
        return ilist

import healpy as hp
        hpx_out = self.geom.to_swapped()
        map_out = self.__class__(hpx_out)
        idx = list(self.geom.get_idx())
        vals = self.get_by_idx(idx)
        msk = vals > 0
        idx = [t[msk] for t in idx]
        vals = vals[msk]

        if self.geom.nside.size > 1:
            nside = self.geom.nside[idx[1:]]
        else:
            nside = self.geom.nside

        if self.geom.nest:
            idx_new = tuple([hp.nest2ring(nside, idx[0])] + idx[1:])
        else:
            idx_new = tuple([hp.ring2nest(nside, idx[0])] + idx[1:])

        map_out.set_by_pix(idx_new, vals)
        return map_out

lon, lat = float(tokens[1]), float(tokens[2])
            radius = np.radians(float(tokens[3]))
            vec = coords_to_vec(lon, lat)[0]
            ilist = hp.query_disc(nside, vec, radius, inclusive=False, nest=nest)
        elif reg_type == "DISK_INC":
            lon, lat = float(tokens[1]), float(tokens[2])
            radius = np.radians(float(tokens[3]))
            vec = coords_to_vec(lon, lat)[0]
            fact = int(tokens[4])
            ilist = hp.query_disc(
                nside, vec, radius, inclusive=True, nest=nest, fact=fact
            )
        elif reg_type == "HPX_PIXEL":
            nside_pix = int(tokens[2])
            if tokens[1] == "NESTED":
                ipix_ring = hp.nest2ring(nside_pix, int(tokens[3]))
            elif tokens[1] == "RING":
                ipix_ring = int(tokens[3])
            else:
                raise ValueError(f"Invalid ordering scheme: {tokens[1]!r}")
            ilist = match_hpx_pix(nside, nest, nside_pix, ipix_ring)
        else:
            raise ValueError(f"Invalid region type: {reg_type!r}")

        return ilist

from ..bayestar.sky_map import derasterize
        if not m.meta['nest']:
            m = m[hp.nest2ring(nside, np.arange(npix))]
        m = derasterize(m)
        m.meta.pop('nest', None)

    if 'UNIQ' not in m.colnames:
        npix = len(m)
        nside = hp.npix2nside(npix)

        if nest is None:
            pass
        elif m.meta['nest'] and not nest:
            m = m[hp.ring2nest(nside, np.arange(npix))]
        elif not m.meta['nest'] and nest:
            m = m[hp.nest2ring(nside, np.arange(npix))]

    if moc:
        return m
    elif distances:
        return tuple(
            np.asarray(m[name]) for name in DEFAULT_NESTED_NAMES), m.meta
    else:
        return np.asarray(m[DEFAULT_NESTED_NAMES[0]]), m.meta

for row in rows:
                key, _, _, _, from_fits = row
                if from_fits is not None:
                    m.meta[key] = from_fits(value)

    if 'UNIQ' not in m.colnames:
        m = Table([col.ravel() for col in m.columns.values()], meta=m.meta)

    if 'UNIQ' in m.colnames and not moc:
        from ..bayestar.sky_map import rasterize
        m = rasterize(m)
        m.meta['nest'] = True
    elif 'UNIQ' not in m.colnames and moc:
        from ..bayestar.sky_map import derasterize
        if not m.meta['nest']:
            m = m[hp.nest2ring(nside, np.arange(npix))]
        m = derasterize(m)
        m.meta.pop('nest', None)

    if 'UNIQ' not in m.colnames:
        npix = len(m)
        nside = hp.npix2nside(npix)

        if nest is None:
            pass
        elif m.meta['nest'] and not nest:
            m = m[hp.ring2nest(nside, np.arange(npix))]
        elif not m.meta['nest'] and nest:
            m = m[hp.nest2ring(nside, np.arange(npix))]

    if moc:
        return m

"""

        tokens = parse_hpxregion(region)
        if tokens[0] == 'DISK':
            vec = coords_to_vec(float(tokens[1]), float(tokens[2]))
            ilist = hp.query_disc(nside, vec[0], np.radians(float(tokens[3])),
                                  inclusive=False, nest=nest)
        elif tokens[0] == 'DISK_INC':
            vec = coords_to_vec(float(tokens[1]), float(tokens[2]))
            ilist = hp.query_disc(nside, vec[0], np.radians(float(tokens[3])),
                                  inclusive=True, fact=int(tokens[4]),
                                  nest=nest)
        elif tokens[0] == 'HPX_PIXEL':
            nside_pix = int(tokens[2])
            if tokens[1] == 'NESTED':
                ipix_ring = hp.nest2ring(nside_pix, int(tokens[3]))
            elif tokens[1] == 'RING':
                ipix_ring = int(tokens[3])
            else:
                raise Exception(
                    "Did not recognize ordering scheme %s" % tokens[1])
            ilist = match_hpx_pixel(nside, nest, nside_pix, ipix_ring)
        else:
            raise Exception(
                "HPX.get_index_list did not recognize region type %s" % tokens[0])
        return ilist