docs: def get_corrector_f(rinput, meta, ins, datamodel):
      """Corrector for intensity flat"""
      from emirdrp.processing.flatfield import FlatFieldCorrector
      flat_info = meta['master_flat']
      with rinput.master_flat.open() as hdul:
          _logger.info('loading intensity flat')
          _logger.debug('flat info: %s', flat_info)
          mflat = hdul[0].data
          # Check NaN and Ceros
          mask1 = mflat < 0
          mask2 = ~numpy.isfinite(mflat)
          if numpy.any(mask1):
              _logger.warning('flat has %d values below 0', mask1.sum())
          if numpy.any(mask2):
              _logger.warning('flat has %d NaN', mask2.sum())
          flat_corrector = FlatFieldCorrector(mflat,
                                              datamodel=datamodel,
                                              calibid=datamodel.get_imgid(hdul))
  
      return flat_corrector