code: def bilinear_interpolation_weights(self, lon, lat):
          
          return bilinear_interpolation_weights(lon, lat, self.nside, order=self.order)
docs: Get the four neighbours for each (lon, lat) position and the weight
          associated with each one for bilinear interpolation.
  
          Parameters
          ----------
          lon, lat : :class:`~astropy.units.Quantity`
              The longitude and latitude values as
              :class:`~astropy.units.Quantity` instances with angle units.
  
          Returns
          -------
          indices : `~numpy.ndarray`
              2-D array with shape (4, N) giving the four indices to use for the
              interpolation
          weights : `~numpy.ndarray`
              2-D array with shape (4, N) giving the four weights to use for the
              interpolation