system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
/// @notice Locate the owner of a specific NFT by its unique ID.
/// @dev Queries about NFTs tied to the zero address are not valid and will throw an error.
/// @param _tokenId The unique identifier for the NFT.
/// @return The address of the individual who owns the NFT.

function ownerOf(uint256 _tokenId) external view returns (address);
assistant
/// @notice postcondition _tokenOwner[_tokenId] == _owner
/// @notice postcondition  _owner !=  address(0)
function ownerOf(uint256 _tokenId) public view returns (address owner);