code: def healpix_to_lonlat(self, healpix_index, dx=None, dy=None):
          
          return healpix_to_lonlat(healpix_index, self.nside, dx=dx, dy=dy, order=self.order)
docs: Convert HEALPix indices (optionally with offsets) to longitudes/latitudes
  
          Parameters
          ----------
          healpix_index : `~numpy.ndarray`
              1-D array of HEALPix indices
          dx, dy : `~numpy.ndarray`, optional
              1-D arrays of offsets inside the HEALPix pixel, which must be in
              the range [0:1] (0.5 is the center of the HEALPix pixels). If not
              specified, the position at the center of the pixel is used.
  
          Returns
          -------
          lon : :class:`~astropy.coordinates.Longitude`
              The longitude values
          lat : :class:`~astropy.coordinates.Latitude`
              The latitude values