public function getExcludeUserIds()
    {
        $userIds = array();
        $currentGroupId = -1;
        //First of all we need to test if subject is group or user
        //In case of group we need to exclude all these users that already exist in role
        if ($this->receiverGroup !== null) {
            $currentGroupId = $this->receiverGroup->getId();
            $roleUsers = $this->role->getUsers();
            foreach ($roleUsers as $user) {
                array_push($userIds, $user->getId());
            }
        }

        //For both cases (user or group) we need to exclude all users already enrolled in other groups
        $roleGroups = $this->role->getGroups();

        if ($roleGroups) {
            foreach ($roleGroups as $group) {
                if ($group->getId() != $currentGroupId) {
                    $userIds = array_merge($userIds, $group->getUserIds());
                }
            }
        }
        $userIds = array_unique($userIds);

        return $userIds;
    }