Revert "Deleted useless comments"

This reverts commit 215c917891be4e816680ce5c02059bfa4f875a52.
Revert 215c917..9e2e751

This rolls back to commit 215c917891be4e816680ce5c02059bfa4f875a52.
Revert 709d478..ca31403

This rolls back to commit 709d478ae169b80ea96648d88f5ea336959f01cd.
Revert d34df65..6aa03d1

This rolls back to commit d34df65b2a39a40824d686564d29df4308b1aaa6.