I'm pretty sure that this is part of the code that implements fraud proofs on Arbitrum One, which is one of the few L2s to currently have fraud proofs.

Sequencer side:

https://github.com/OffchainLabs/nitro/blob/d28682b9300d50214...

Contract side:

https://github.com/OffchainLabs/nitro-contracts/blob/90037b9...

It seems to me that Optimism is lagging way behind - I'm not sure if they have fraud proofs yet even to this day. I consider Arbitrum to have "picked up the torch" so-to-say.