code: public static boolean isKeyUsed(final Jedis jedis, final String key) {
          return !NONE.equalsIgnoreCase(jedis.type(key));
      }
docs: Determines if the queue identified by the given key is used.
  
  @param jedis
  connection to Redis
  @param key
  the key that identifies a queue
  @return true if the key is used, false otherwise