mapping(bytes32 => boolean) public usedHash

    function validatePaymasterUserOp(UserOperation calldata userOp, bytes32 /*userOpHash*/, uint256 requiredPreFund)
    external override returns (bytes memory context, uint256 deadline) {
        (requiredPreFund);
        bytes32 hash = getHash(userOp);
        require(!usedHash[hash], "used hash");
        usedHash[hash] = true;
