static function removeFromPool($object_or_pk) {
		$pool_key = $object_or_pk instanceof Model ? implode('-', $object_or_pk->getPrimaryKeyValues()) : $object_or_pk;

		if (isset(static::$_instancePool[$pool_key])) {
			unset(static::$_instancePool[$pool_key]);
			--static::$_instancePoolCount;
		}
	}