code: def load_hdu(self, imname, hdulist, num_hdu):
          
          buf_io = BytesIO()
          hdulist.writeto(buf_io)
  
          load_fits_buffer = self._client.lookup_attr('load_fits_buffer')
  
          return load_fits_buffer(imname, self._chname,
                                  Blob(buf_io.getvalue()),
                                  num_hdu, {})
docs: Display an astropy.io.fits HDU in a remote Ginga reference viewer.
  
          Parameters
          ----------
          imname : str
              A name to use for the image in the reference viewer.
  
          hdulist : `~astropy.io.fits.HDUList`
              This should be a valid HDUList loaded via the `astropy.io.fits` module.
  
          num_hdu : int or 2-tuple
              Number or key of the HDU to open from the `HDUList`.
  
          Returns
          -------
          0
  
          Notes
          -----
          * The "RC" plugin needs to be started in the viewer for this to work.