public function addCss($asset)
    {
        return $this->addType(Assets::CSS_COLLECTION,Assets::CSS_TYPE, $asset, $this->unifyLegacyArguments(\func_get_args(), Assets::CSS_TYPE));
    }
public function addCss($asset)
    {
        return $this->addType(Assets::CSS_COLLECTION,Assets::CSS_TYPE, $asset, $this->unifyLegacyArguments(\func_get_args(), Assets::CSS_TYPE));
    }
public function addCss ( $ asset ) { return $ this -> addType ( Assets :: CSS_COLLECTION , Assets :: CSS_TYPE , $ asset , $ this -> unifyLegacyArguments ( \ func_get_args ( ) , Assets :: CSS_TYPE ) ) ; }
Add a CSS asset or a collection of assets.

@return $this
Add a CSS asset or a collection of assets .