def cached_method(method=None, ttl=300):
    print method, ttl
    if method is None:
        return lambda m: cached_method(m, ttl)
    def cached_func(self, *args, **kwargs):
        ctx = md5_constructor()
        [ctx.update(str(i)) for i in args]
        [ctx.update('%s=%s' % (k,v)) for k,v in kwargs.iteritems()]
        key = 'cmethod.%s.%s.%s.%s' % (self.__class__.__name__, method.__name__, ctx.hexdigest(), ttl)
        
        result = cache.get(key)
        if not result:
            result = method(self, *args, **kwargs)
            cache.set(key, result, ttl)
        return result
    return cached_func


# А вызывать
@cached_method(ttl=500)
def genre_cloud(self, steps=4):
     pass
# или
@cached_method
def genre_cloud(self, steps=4):
     pass