docs: def filter_tag(arg):
      """ Parses a --filter-tag argument """
      try:
          strip_len = len('Key=')
          key, value = arg[strip_len:].split(',Value=', 1)
          return key, value
      except:
          msg = 'Invalid --filter-tag argument: {}'
          raise argparse.ArgumentTypeError(msg.format(arg))