old_contents: from redis_cache.cache import RedisCache as PlainRedisCache
  from redis_lock import Lock
  
  
  class RedisCache(PlainRedisCache):
      def lock(self, key, expire=None):
          return Lock(self.client, key, expire=expire)
  
new_contents: from redis_cache.cache import RedisCache as PlainRedisCache
  from redis_lock import Lock
  
  
  class RedisCache(PlainRedisCache):
      def lock(self, key, expire=None):
          return Lock(self.client.client, key, expire=expire)
  
subject: Use actual client.