code: def _updateKW(image, filename, exten, skyKW, Value):
      
      # Update the value in memory
      image.header[skyKW] = Value
  
      # Now update the value on disk
      if isinstance(exten,tuple):
          strexten = '[%s,%s]'%(exten[0],str(exten[1]))
      else:
          strexten = '[%s]'%(exten)
      log.info('Updating keyword %s in %s' % (skyKW, filename + strexten))
      fobj = fileutil.openImage(filename, mode='update', memmap=False)
      fobj[exten].header[skyKW] = (Value, 'Sky value computed by AstroDrizzle')
      fobj.close()
docs: update the header with the kw,value