contract ERC721 is ERC165, ERC721Events {

  function balanceOf(address _owner) external view returns (uint256 _balance);
  function ownerOf(uint256 _tokenId) external view returns (address _owner);
//   function exists(uint256 _tokenId) external view returns (bool _exists);

  function approve(address _to, uint256 _tokenId) external;
  function getApproved(uint256 _tokenId)
    external view returns (address _operator);

  function setApprovalForAll(address _operator, bool _approved) external;
  function isApprovedForAll(address _owner, address _operator)
    external view returns (bool);

  function transferFrom(address _from, address _to, uint256 _tokenId) external;
  function safeTransferFrom(address _from, address _to, uint256 _tokenId)
    external;

  function safeTransferFrom(
    address _from,
    address _to,
    uint256 _tokenId,
    bytes calldata _data
  )
    external;
}
/*interface*/
function approve(address _to, uint256 _tokenId) external;
//   function exists(uint256 _tokenId) external view returns (bool _exists);