public function getGroupList($from = null)
{
$params = array();
if ($from !== null) {
$params['from'] = $from;
}
$data = $this->__preparedRequest('group_list', 'GET', $params);
$groups = (array) $data->results;
$result = array();
foreach ($groups as $group) {
$result[] = new Group($group->id, $this);
}
return $result;
}