system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
/// @notice Retrieve the designated address allowed to manage the specified NFT.
/// @dev Throws an error if _tokenId does not correspond to a valid NFT.
/// @param _tokenId The NFT identifier to find the approved address for.
/// @return The approved address, or the zero address if no approval exists.

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);