public function getStyleSheetXml()
    {
        $fontsXml = $this->getComponentXml($this->fonts);
        $fillsXml = $this->getComponentXml($this->fills);
        $bordersXml = $this->getComponentXml($this->borders);
        $cellXfsXml = $this->getComponentXml($this->styles);

        return sprintf(StyleXml::STYLE_SHEET_XML,
            sprintf(StyleXml::FONTS_XML, count($this->fonts), $fontsXml),
            sprintf(StyleXml::FILLS_XML, count($this->fills), $fillsXml),
            sprintf(StyleXml::BORDERS_XML, count($this->borders), $bordersXml),
            sprintf(StyleXml::CELL_XFS_XML, count($this->styles), $cellXfsXml)
        );
    }