def _get_cache_key(self):
        keys = list(self.params.keys())
        keys.sort()
        cache_key = str()
        for key in keys:
            if key != "api_sig" and key != "api_key" and key != "sk":
                cache_key += key + self.params[key]
        return hashlib.sha1(cache_key.encode("utf-8")).hexdigest()