code: def _get_solar_flux(self, band):
          
          solar_flux = self.cal['solar_flux'].isel(bands=band).values
          d_index = self.cal['detector_index'].fillna(0).astype(int)
  
          return da.map_blocks(self._get_items, d_index.data, solar_flux=solar_flux, dtype=solar_flux.dtype)
docs: Get the solar flux for the band.