Whoops \ Exception \ ErrorException (E_ERROR)

Call to undefined method JModuleHelper::getModuleList()
Open: C:\xampp\htdocs\testing\libraries\gantry5\classes\Gantry\Framework\Platform.php

        $modules = $this->getModuleList();
        return $id && isset($modules[$id]) ? $modules[$id] : null;
    }
 
    protected function &getModuleList()
    {
        if ($this->modules === null) {
            $modules = \JModuleHelper::getModuleList();
 
            $this->modules = [];