How to use the urlpath.MultiDictMixin function in urlpath

class MultiDictMixin:
    def get_one(self, key, default=None, predicate=None, type=None):
        # `predicate` comes from `inspect.getmembers`.
        try:
            values = self[key]
        except LookupError:
            pass
        else:
            for value in values:
                if not predicate or predicate(value):
                    return value if not type else type(value)

        return default


class FrozenMultiDict(MultiDictMixin, FrozenDict):
    pass


def cached_property(getter):
    """Limited version of `functools.lru_cache`. But `__hash__` is not required.
    """

    @functools.wraps(getter)
    def helper(self):
        key = '_cached_property_' + getter.__name__

        if key in self.__dict__:
            return self.__dict__[key]

        result = self.__dict__[key] = getter(self)
        return result