How to use the multimethod.__init__.DispatchError function in multimethod

def __call__(self, *args, **kwargs):
        """Dispatch to first matching function."""
        for sig, func in reversed(self.items()):
            arguments = sig.bind(*args, **kwargs).arguments
            if all(predicate(arguments[name]) for name, predicate in func.__annotations__.items()):
                return func(*args, **kwargs)
        raise DispatchError("No matching functions found")

def __missing__(self, types: tuple) -> Callable:
        """Find and cache the next applicable method of given types."""
        self.evaluate()
        if types in self:
            return self[types]
        groups = groupby(signature(types).__sub__, self.parents(types))
        keys = groups[min(groups)] if groups else []
        funcs = {self[key] for key in keys}
        if len(funcs) == 1:
            return self.setdefault(types, *funcs)
        msg = f"{self.__name__}: {len(keys)} methods found"  # type: ignore
        raise DispatchError(msg, types, keys)