code: def mag_to_fnu(self, mag):
          
          if self.native_flux_kind == 'flam':
              return flam_ang_to_fnu_cgs(self.mag_to_flam(mag), self.pivot_wavelength())
          raise PKError('dont\'t know how to get f_ν from mag for bandpass %s/%s',
                        self.telescope, self.band)
docs: Convert a magnitude in this band to a f_ν flux density.
  
          It is assumed that the magnitude has been computed in the appropriate
          photometric system. The definition of "appropriate" will vary from
          case to case.