code: def _appendTrlFile(trlfile,drizfile):
      
      if not os.path.exists(drizfile):
          return
      # Open already existing CALWF3 trailer file for appending
      ftrl = open(trlfile,'a')
      # Open astrodrizzle trailer file
      fdriz = open(drizfile)
  
      # Read in drizzle comments
      _dlines = fdriz.readlines()
  
      # Append them to CALWF3 trailer file
      ftrl.writelines(_dlines)
  
      # Close all files
      ftrl.close()
      fdriz.close()
  
      # Now, clean up astrodrizzle trailer file
      os.remove(drizfile)
docs: Append drizfile to already existing trlfile from CALXXX.