src/Writer.php
private function getAttributeName($key)
    {
        if (0 === strpos($key, '@') && $this->isValidNodeName($attrName = substr($key, 1))) {
            return $attrName;
        }

        return null;
    }
private function getAttributeName($key)
    {
        if (0 === strpos($key, '@') && $this->isValidNodeName($attrName = substr($key, 1))) {
            return $attrName;
        }

        return null;
    }
private function getAttributeName ( $ key ) { if ( 0 === strpos ( $ key , '@' ) && $ this -> isValidNodeName ( $ attrName = substr ( $ key , 1 ) ) ) { return $ attrName ; } return null ; }
Extracts the raw attribute indicator.

@param string $key string with leading `@`.

@return string
Extracts the raw attribute indicator .