Solved Some questions about Chests

are chests tiles saved in chunks, right ?
if yes, where in the code ?

when a chest is broke, why the tile isn't "closed" ?
https://github.com/PocketMine/PocketMine-MP/blob/master/src/pocketmine/block/Chest.php#L128

i noticed that the tile is deleted/closed when the chest is broke but where?

https://github.com/PocketMine/PocketMine-MP/blob/master/src/pocketmine/tile/Chest.php#L246
wow , so single chests aren't deleted? because if is not paired , return false ... -.-

Good question. I did some further research, and I found this:
https://github.com/PocketMine/PocketMine-MP/blob/master/src/pocketmine/level/Level.php#L1599
So, it is not the Block's responsibility to remove a tile associated with it. So, even if the block is replaced by another block (other than chest), as long as it is broken properly, the tile will be broken/removed along with the block.

Thanks A LOT