code: def do_filter(config, config_dir):
      
      if not os.path.exists(config_dir):
          print "Configuration '{}' does not exist.".format(config)
          exit(1)    
  
      editor = os.environ["EDITOR"]
  
      config_filter = os.path.join(config_dir, 'filter')
      call([editor, config_filter])
      print "Filter configuration has been updated."
docs: CLI action "run editor for filters list".