public static function get_reviewer_assessments($workshopid, $userid = 0) {
        global $USER, $DB, $PAGE;

        $params = self::validate_parameters(
            self::get_reviewer_assessments_parameters(), array('workshopid' => $workshopid, 'userid' => $userid)
        );
        $warnings = $assessments = array();

        // Get and validate the submission and workshop.
        list($workshop, $course, $cm, $context) = self::validate_workshop($params['workshopid']);

        // Extra checks so only users with permissions can view other users assessments.
        if (empty($params['userid']) || $params['userid'] == $USER->id) {
            $userid = $USER->id;
            list($assessed, $notice) = $workshop->check_examples_assessed_before_assessment($userid);
            if (!$assessed) {
                throw new moodle_exception($notice, 'mod_workshop');
            }
            if ($workshop->phase < workshop::PHASE_ASSESSMENT) {    // Can view assessments only in assessment phase onwards.
                throw new moodle_exception('nopermissions', 'error', '', 'view assessments');
            }
        } else {
            require_capability('mod/workshop:viewallassessments', $context);
            $user = core_user::get_user($params['userid'], '*', MUST_EXIST);
            core_user::require_active_user($user);
            if (!$workshop->check_group_membership($user->id)) {
                throw new moodle_exception('notingroup');
            }
            $userid = $user->id;
        }
        // Now get all my assessments (includes those pending review).
        $assessmentsrecords = $workshop->get_assessments_by_reviewer($userid);

        $related = array('context' => $context);
        foreach ($assessmentsrecords as $assessment) {
            $assessment = self::prepare_assessment_for_external($assessment, $workshop);
            if (empty($assessment)) {
                continue;
            }
            $exporter = new assessment_exporter($assessment, $related);
            $assessments[] = $exporter->export($PAGE->get_renderer('core'));
        }

        return array(
            'assessments' => $assessments,
            'warnings' => $warnings
        );
    }