def url_decode(s, charset='utf-8', decode_keys=False, include_empty=True,
               errors='replace', separator='&', cls=None):
    """Parse a querystring and return it as :class:`MultiDict`.  Per default
    only values are decoded into unicode strings.  If `decode_keys` is set to
    `True` the same will happen for keys.

    Per default a missing value for a key will default to an empty key.  If
    you don't want that behavior you can set `include_empty` to `False`.

    Per default encoding errors are ignored.  If you want a different behavior
    you can set `errors` to ``'replace'`` or ``'strict'``.  In strict mode a
    `HTTPUnicodeError` is raised.

    .. versionchanged:: 0.5
       In previous versions ";" and "&" could be used for url decoding.
       This changed in 0.5 where only "&" is supported.  If you want to
       use ";" instead a different `separator` can be provided.

       The `cls` parameter was added.

    :param s: a string with the query string to decode.
    :param charset: the charset of the query string.
    :param decode_keys: set to `True` if you want the keys to be decoded
                        as well.
    :param include_empty: Set to `False` if you don't want empty values to
                          appear in the dict.
    :param errors: the decoding error behavior.
    :param separator: the pair separator to be used, defaults to ``&``
    :param cls: an optional dict class to use.  If this is not specified
                       or `None` the default :class:`MultiDict` is used.
    """
    if cls is None:
        cls = MultiDict
    return cls(_url_decode_impl(str(s).split(separator), charset, decode_keys,
                                include_empty, errors))