public function manyToMany($to_table, $join_table, $from_column = null, $from_join_column = null, $to_join_column = null, $to_column = null)
{
$to_table = new Table($to_table, true, $this);
$join_table = new Table($join_table, false, $this);
return new Association\ManyToMany($to_table, $join_table, $from_column, $from_join_column, $to_join_column, $to_column);
}