code: def _process_input_wcs_single(fname, wcskey, updatewcs):
      
      if wcskey in ['', ' ', 'INDEF', None]:
          if updatewcs:
              uw.updatewcs(fname, checkfiles=False)
      else:
          numext = fileutil.countExtn(fname)
          extlist = []
          for extn in range(1, numext + 1):
              extlist.append(('SCI', extn))
          if wcskey in string.ascii_uppercase:
              wkey = wcskey
              wname = ' '
          else:
              wname = wcskey
              wkey = ' '
          altwcs.restoreWCS(fname, extlist, wcskey=wkey, wcsname=wname)
      # make an asn table at the end
      # Make sure there is a WCSCORR table for each input image
      if wcskey not in ['', ' ', 'INDEF', None] or updatewcs:
          wcscorr.init_wcscorr(fname)
docs: See docs for _process_input_wcs.
      This is separated to be spawned in parallel.