def parse(self, argument):
    """Parses the string argument and returns the native value.

    By default it returns its argument unmodified.

    Args:
      argument: string argument passed in the commandline.

    Raises:
      ValueError: Raised when it fails to parse the argument.
      TypeError: Raised when the argument has the wrong type.

    Returns:
      The parsed value in native type.
    """
    if not isinstance(argument, six.string_types):
      raise TypeError('flag value must be a string, found "{}"'.format(
          type(argument)))
    return argument
Parses the string argument and returns the native value.

    By default it returns its argument unmodified.

    Args:
      argument: string argument passed in the commandline.

    Raises:
      ValueError: Raised when it fails to parse the argument.
      TypeError: Raised when the argument has the wrong type.

    Returns:
      The parsed value in native type.