_helpers.py 文件源码

def _from_bytes(value):
    """Converts bytes to a string value, if necessary.

    Args:
        value: The string/bytes value to be converted.

    Returns:
        The original value converted to unicode (if bytes) or as passed in
        if it started out as unicode.

    Raises:
        ValueError if the value could not be converted to unicode.
    """
    result = (value.decode('utf-8')
              if isinstance(value, six.binary_type) else value)
    if isinstance(result, six.text_type):
        return result
    else:
        raise ValueError(
            '{0!r} could not be converted to unicode'.format(value))