Trusted proof of data from a datasource using Oraclize

OraclizeAgeOfPresidentProof.sol

pragma solidity ^0.4.0;
import "github.com/oraclize/ethereum-api/oraclizeAPI.sol";
contract OraclizeAgeOfPresidentProof is usingOraclize {
    string public result;
    constructor() {
        oraclize_setProof(proofType_Android | proofStorage_IPFS);
        oraclize_setCustomGasPrice(2 * 1000000000);
    }
    
    function update() payable {
        oraclize_query("nested", "[WolframeAlpha] Age of ${[WolframeAlpha] Current US president}", 180000);
    }
    
    function __callback(bytes32 _queryId, string _r, bytes _p) {
        require(msg.sender == oraclize_cbAddress());
        result = _r;
    }
}