code: def hdu_list(self):
          
          hdu_list = fits.HDUList()
  
          hdu = _table_to_bintable(self.source_table)
          hdu.name = 'sources'
          hdu_list.append(hdu)
  
          hdu = _table_to_bintable(self.event_table)
          hdu.name = 'events'
          hdu_list.append(hdu)
  
          hdu = self.image
          hdu.name = 'image'
          hdu_list.append(hdu)
  
          return hdu_list
docs: HDU list (`~astropy.io.fits.HDUList`).
  
          Different pieces collected together in a HDU list.
  
          This method makes it easy to write the example dataset to a FITS
          file with multiple HDUs.