system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
/// @notice Obtain the address authorized to act on behalf of the specified NFT.
/// @dev This function will revert if _tokenId does not reference a valid NFT.
/// @param _tokenId Identifier of the NFT to query the approval for.
/// @return The address authorized for this NFT, or zero 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);