protected function extractRelevantInfo()
    {
        $this->customNumberFormats = [];
        $this->stylesAttributes = [];

        $xmlReader = new XMLReader();

        if ($xmlReader->openFileInZip($this->filePath, self::STYLES_XML_FILE_PATH)) {
            while ($xmlReader->read()) {
                if ($xmlReader->isPositionedOnStartingNode(self::XML_NODE_NUM_FMTS)) {
                    $this->extractNumberFormats($xmlReader);

                } else if ($xmlReader->isPositionedOnStartingNode(self::XML_NODE_CELL_XFS)) {
                    $this->extractStyleAttributes($xmlReader);
                }
            }

            $xmlReader->close();
        }
    }