private function getGroupId(): ?string
    {
        $group = $this->getPanelGroup();
        if (!$group) {
            return null;
        }

        $cssID = StringUtil::deserialize($group->cssID, true);
        if (is_string($cssID[0]) && $cssID[0] !== '') {
            return $cssID[0];
        }

        return 'panel-group-' . $group->id;
    }
private function getGroupId(): ?string
    {
        $group = $this->getPanelGroup();
        if (!$group) {
            return null;
        }

        $cssID = StringUtil::deserialize($group->cssID, true);
        if (is_string($cssID[0]) && $cssID[0] !== '') {
            return $cssID[0];
        }

        return 'panel-group-' . $group->id;
    }
private function getGroupId ( ) : ? string { $ group = $ this -> getPanelGroup ( ) ; if ( ! $ group ) { return null ; } $ cssID = StringUtil :: deserialize ( $ group -> cssID , true ) ; if ( is_string ( $ cssID [ 0 ] ) && $ cssID [ 0 ] !== '' ) { return $ cssID [ 0 ] ; } return 'panel-group-' . $ group -> id ; }
Get the panel group id.

@return string
Get the panel group id .