protected function get_relation_array($relation_info, $primary_key_value = null, $limit = null)
{
list($field_name, $related_table, $related_field_title, $where_clause, $order_by) = $relation_info;
if ($primary_key_value !== null) {
$primary_key = $this->basic_model->get_primary_key($related_table);
//A where clause with the primary key is enough to take the selected key row
$where_clause = array($primary_key => $primary_key_value);
}
$relation_array = $this->basic_model->get_relation_array($field_name, $related_table, $related_field_title, $where_clause, $order_by, $limit);
return $relation_array;
}