Devise\Templates\TemplatesRepository::splitVarsAndNewVars PHP Method

    private function splitVarsAndNewVars($template)
    {
        foreach ($template['vars'] as $varName => $varVal) {
            if (is_null($varVal)) {
                // add varName to newVars array
                $template['newVars'][$varName] = NULL;
                // unset/remove key from template vars array
                unset($template['vars'][$varName]);
            }
        }
        return $template;
    }