def unquote_header_value(value: str) -> str:
    """Remove double quotes and decode slash-escaped ``"`` and ``\\`` characters in a
    header value.

    This is the reverse of :func:`quote_header_value`.

    :param value: The header value to unquote.

    .. versionchanged:: 3.0
        The ``is_filename`` parameter is removed.
    """
    if len(value) >= 2 and value[0] == value[-1] == '"':
        value = value[1:-1]
        return value.replace("\\\\", "\\").replace('\\"', '"')

    return value
Remove double quotes and decode slash-escaped ``"`` and ``\`` characters in a
    header value.

    This is the reverse of :func:`quote_header_value`.

    :param value: The header value to unquote.

    .. versionchanged:: 3.0
        The ``is_filename`` parameter is removed.
    
src/werkzeug/http.py