public RedisOutputFormat finish() {
            if (redisOutputFormat.url == null) {
                throw new IllegalArgumentException("No URL supplied.");
            }

            if (redisOutputFormat.tableName == null) {
                throw new IllegalArgumentException("No tablename supplied.");
            }

            return redisOutputFormat;
        }
1. build key from map.
 2. save key and value.
 3. set expired time for key when keyExpiredTime has been set.
@param refData
redis5/redis5-sink/src/main/java/com/dtstack/flink/sql/sink/redis/RedisOutputFormat.java