There are numerous instances throughout the codebase in different contracts. Heres just one of the specific instances:  
https://github.com/nounsDAO/nouns-monorepo/blob/718211e063d511eeda1084710f6a682955e80dcb/packages/nouns-contracts/contracts/governance/NounsDAOLogicV2.sol#L61
https://github.com/nounsDAO/nouns-monorepo/blob/718211e063d511eeda1084710f6a682955e80dcb/packages/nouns-contracts/contracts/governance/NounsDAOLogicV2.sol#L218
There are numerous instances throughout the codebase in different contracts. Heres just one of the specific instances:  
https://github.com/nounsDAO/nouns-monorepo/blob/718211e063d511eeda1084710f6a682955e80dcb/packages/nouns-contracts/contracts/governance/NounsDAOLogicV2.sol#L901
https://github.com/nounsDAO/nouns-monorepo/blob/718211e063d511eeda1084710f6a682955e80dcb/packages/nouns-contracts/contracts/governance/NounsDAOLogicV3.sol#L19
https://github.com/nounsDAO/nouns-monorepo/blob/718211e063d511eeda1084710f6a682955e80dcb/packages/nouns-contracts/contracts/governance/NounsDAOInterfaces.sol#L217
https://github.com/nounsDAO/nouns-monorepo/blob/718211e063d511eeda1084710f6a682955e80dcb/packages/nouns-contracts/contracts/governance/fork/newdao/token/base/ERC721CheckpointableUpgradeable.sol#L80-L84
