protected function getCallback()
    {
        if (!isset(self::$client)) {
            self::$client = new TraceClient($this->clientConfig);
        }

        return [self::$client, $this->batchMethod];
    }
protected function getCallback()
    {
        if (!isset(self::$client)) {
            self::$client = new TraceClient($this->clientConfig);
        }

        return [self::$client, $this->batchMethod];
    }
protected function getCallback ( ) { if ( ! isset ( self :: $ client ) ) { self :: $ client = new TraceClient ( $ this -> clientConfig ) ; } return [ self :: $ client , $ this -> batchMethod ] ; }
Returns an array representation of a callback which will be used to write
batch items.

@return array
Returns an array representation of a callback which will be used to write batch items .