function __callback(bytes32 myid, string memory result, bytes memory proof) public {
        if (msg.sender != oraclize_cbAddress()) revert();
        require (pendingQueries[myid] == true);
        proof;
        emit NewKrakenPriceTicker(result);
        uint USD = parseInt(result);
        uint tokenPriceInWei = (1 ether / USD) / 100; 
        _rate = 1 ether / tokenPriceInWei;
        updatePrice();
        delete pendingQueries[myid];
    }