code: def _is_flag_file_directive(self, flag_string):
      
      if isinstance(flag_string, type('')):
        if flag_string.startswith('--flagfile='):
          return 1
        elif flag_string == '--flagfile':
          return 1
        elif flag_string.startswith('-flagfile='):
          return 1
        elif flag_string == '-flagfile':
          return 1
        else:
          return 0
      return 0
docs: Checks whether flag_string contain a --flagfile=<foo> directive.