_isRedisReady() {
    if (!this._rejectIfRedisNotReady) {
      return true;
    }
    // ioredis client
    if (this.client.status && this.client.status !== 'ready') {
      return false;
    }
    // node-redis client
    if (typeof this.client.isReady === 'function' && !this.client.isReady()) {
      return false;
    }
    return true;
  }
Prevent actual redis call if redis connection is not ready
Because of different connection state checks for ioredis and node-redis, only this clients would be actually checked.
For any other clients all the requests would be passed directly to redis client
@return {boolean}
@private