private function getIssuesToGroup(array $issues) : array
    {
        return array_filter($issues, static function (Issue $issue) : bool {
            return (! $issue->isPullRequest() && $issue->getLinkedPullRequest() !== null) === false;
        });
    }
private function getIssuesToGroup(array $issues) : array
    {
        return array_filter($issues, static function (Issue $issue) : bool {
            return (! $issue->isPullRequest() && $issue->getLinkedPullRequest() !== null) === false;
        });
    }
@param Issue[] $issues

@return Issue[]