system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
/// @notice Retrieve the approved address for managing a given NFT.
/// @dev This function reverts if _tokenId does not map to a valid NFT.
/// @param _tokenId The identifier of the NFT to query for approval.
/// @return The approved address for the NFT, or the zero address if none 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);