protected function getInheritedPrivileges(array $parents)
    {
        if (! $parents) {
            return array();
        }

        $rolePrivileges = $this->acl->getRolePrivileges();
        $inherited      = array();
        foreach ($parents as $parent) {
            if (isset($rolePrivileges[$parent])) {
                $inherited = $inherited + array_flip($rolePrivileges[$parent][\Zend_Acl::TYPE_ALLOW]);
                $inherited = $inherited +
                        array_flip($rolePrivileges[$parent][\MUtil_Acl::INHERITED][\Zend_Acl::TYPE_ALLOW]);
            }
        }
        // Sneaks in:
        unset($inherited[""]);

        return $inherited;
    }