code: def _parse_user_flags():
      
      try:
          idx = list(sys.argv).index('--user-flags')
          user_flags_file = sys.argv[idx + 1]
      except (ValueError, IndexError):
          user_flags_file = ''
  
      if user_flags_file and os.path.isfile(user_flags_file):
          from ryu.utils import _import_module_file
          _import_module_file(user_flags_file)
docs: Parses user-flags file and loads it to register user defined options.