/**
  * @brief get a list of all groups
  * @returns array with group names
  *
  * Returns a list with all groups
  */
 public function getGroups()
 {
     if (!$this->configured) {
         return array();
     }
     if (empty($this->_groups)) {
         $ldap_groups = OC_LDAP::fetchListOfGroups($this->ldapGroupFilter, array(OC_LDAP::conf('ldapGroupDisplayName'), 'dn'));
         $this->_groups = OC_LDAP::ownCloudGroupNames($ldap_groups);
     }
     return $this->_groups;
 }