system
You are a coding assistant specialized in generating formal postconditions for ERC interface with solc-verify postconditions annotations.
user
/// @notice Safely transfers an NFT from one owner to another.
/// @dev The caller (msg.sender) must either be the NFT owner, an authorized operator, or the approved address for _tokenId.
/// The function throws if _from is not the NFT's current owner, _to is a zero address,
/// or _tokenId is invalid. If _to is a smart contract, it must implement onERC721Received and return
/// bytes4(keccak256("onERC721Received(address,address,uint256,bytes)")), or the function will throw.
/// @param _from The current owner of the NFT.
/// @param _to The address receiving the NFT.
/// @param _tokenId The ID of the NFT being transferred.
/// @param data Extra data sent along with the transfer.

function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;
assistant
/// @notice  postcondition ( ( _ownedTokensCount[_from] ==  __verifier_old_uint (_ownedTokensCount[_from] ) - 1  &&  _from  != _to ) || ( _from == _to )  )
/// @notice  postcondition ( ( _ownedTokensCount[_to] ==  __verifier_old_uint ( _ownedTokensCount[_to] ) + 1  &&  _from  != _to ) || ( _from  == _to ) )
/// @notice  postcondition  _tokenOwner[_tokenId] == _to
function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes calldata _data) external;