system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
/// @notice Identify the address that has been approved for a particular NFT.
/// @dev If _tokenId is invalid or not an NFT, the function will revert.
/// @param _tokenId The NFT identifier to find the approved address for.
/// @return The approved address, or zero if no approval has been set.

function getApproved(uint256 _tokenId) external view returns (address);
assistant
/// @notice postcondition _tokenOwner[tokenId] != address(0)
/// @notice postcondition _tokenApprovals[tokenId] == approved
function getApproved(uint256 _tokenId) external view returns (address approved);