/**
  * @return GoogleLineChart
  **/
 public function addLine(GoogleChartLine $line)
 {
     $this->color->addColor($line->getColor());
     $this->legend->addItem($line->getTitle());
     $this->data->addDataSet($line->getValue());
     if ($style = $line->getStyle()) {
         $this->style->addStyle($style);
     }
     if ($labelStyle = $line->getLabelStyle()) {
         $this->labelStyle->addStyle($labelStyle->setDataSetIndex($this->data->getCount() - 1));
     }
     return $this;
 }