code: def ApertureHDU(model):
      '''
      Construct the HDU containing the aperture used to de-trend.
  
      '''
  
      # Get mission cards
      cards = model._mission.HDUCards(model.meta, hdu=3)
  
      # Add EVEREST info
      cards.append(('COMMENT', '************************'))
      cards.append(('COMMENT', '*     EVEREST INFO     *'))
      cards.append(('COMMENT', '************************'))
      cards.append(('MISSION', model.mission, 'Mission name'))
      cards.append(('VERSION', EVEREST_MAJOR_MINOR, 'EVEREST pipeline version'))
      cards.append(('SUBVER', EVEREST_VERSION, 'EVEREST pipeline subversion'))
      cards.append(('DATE', strftime('%Y-%m-%d'),
                    'EVEREST file creation date (YYYY-MM-DD)'))
  
      # Create the HDU
      header = pyfits.Header(cards=cards)
      hdu = pyfits.ImageHDU(data=model.aperture,
                            header=header, name='APERTURE MASK')
  
      return hdf ApertureHDU(model):
      '''
      Construct the HDU containing the aperture used to de-trend.
  
      '''
  
      # Get mission cards
      cards = model._mission.HDUCards(model.meta, hdu=3)
  
      # Add EVEREST info
      cards.append(('COMMENT', '************************'))
      cards.append(('COMMENT', '*     EVEREST INFO     *'))
      cards.append(('COMMENT', '************************'))
      cards.append(('MISSION', model.mission, 'Mission name'))
      cards.append(('VERSION', EVEREST_MAJOR_MINOR, 'EVEREST pipeline version'))
      cards.append(('SUBVER', EVEREST_VERSION, 'EVEREST pipeline subversion'))
      cards.append(('DATE', strftime('%Y-%m-%d'),
                    'EVEREST file creation date (YYYY-MM-DD)'))
  
      # Create the HDU
      header = pyfits.Header(cards=cards)
      hdu = pyfits.ImageHDU(data=model.aperture,
                            header=header, name='APERTURE MASK')
  
      return hdu
docs: Construct the HDU containing the aperture used to de-trend.