public static function getLinkedIssueKey($issueLink)
    {
        $linkedIssueKey = null;

        if (isset($issueLink['outwardIssue'])) {
            if (isset($issueLink['outwardIssue']['key'], $issueLink['type']['outward'])) {
                $linkedIssueKey = $issueLink['outwardIssue']['key'];
            }
        } elseif (isset($issueLink['inwardIssue'], $issueLink['type']['inward'])) {
            if (isset($issueLink['inwardIssue']['key'])) {
                $linkedIssueKey = $issueLink['inwardIssue']['key'];
            }
        }

        return $linkedIssueKey;
    }