public function group_start($not = '', $type = 'AND ')
{
$type = $this->_group_get_type($type);
$this->qb_where_group_started = TRUE;
$prefix = count($this->qb_where) === 0 && count($this->qb_cache_where) === 0 ? '' : $type;
$where = array('condition' => $prefix . $not . str_repeat(' ', ++$this->qb_where_group_count) . ' (', 'escape' => FALSE);
$this->qb_where[] = $where;
if ($this->qb_caching) {
$this->qb_cache_where[] = $where;
}
return $this;
}