code: def ring_to_nested(ring_index, nside):
      
  
      nside = np.asarray(nside, dtype=np.intc)
  
      return _core.ring_to_nested(ring_index, nside)
docs: Convert a HEALPix 'ring' index to a HEALPix 'nested' index
  
      Parameters
      ----------
      ring_index : int or `~numpy.ndarray`
          Healpix index using the 'ring' ordering
      nside : int or `~numpy.ndarray`
          Number of pixels along the side of each of the 12 top-level HEALPix tiles
  
      Returns
      -------
      nested_index : int or `~numpy.ndarray`
          Healpix index using the 'nested' ordering