Cannot see OFAC filter implemented within the source code

Hi Team, Within the given Relay source code (GitHub - flashbots/mev-boost-relay: MEV-Boost Relay for Ethereum proposer/builder separation (PBS)), I cannot find OFAC filtering implemented. I am planning to deploy a Relay using this source code. My question is, How to implement the OFAC filtering within the Relay to the blocks submitted by block builders ? Any help is appreciated. Thanks.