code: def extract_gti_data(hdu_in):
      
      data = hdu_in.data
      exposure = hdu_in.header['EXPOSURE']
      tstop = hdu_in.header['TSTOP']
      return (data, exposure, tstop)
docs: Extract some GTI related data
  
      Parameters
      -------
      hdu_in : `astropy.io.fits.BinTableHDU`
          The GTI data
  
      Returns
      -------
      data : `astropy.io.fits.BinTableHDU` data
  
      exposure : float
          Exposure value taken from FITS header
  
      tstop : float
          TSTOP value taken from FITS header