https://travis-ci.org/github/bitcoin/bitcoin/jobs/680452476#L6107
{
    return RPCHelpMan{"gettxoutproof",
                "\nReturns a hex-encoded proof that \"txid\" was included in a block.\n"
                "\nNOTE: By default this function only works sometimes. This is when there is an\n"
                "unspent output in the utxo for this transaction. To make it always work,\n"
                "you need to maintain a transaction index, using the -txindex command line option or\n"
                "specify the block in which the transaction is included manually (by blockhash).\n",
                {
                    {"txids", RPCArg::Type::ARR, RPCArg::Optional::NO, "The txids to filter",
                        {
                            {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED, "A transaction hash"},
                        },
                        },
                    {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED_NAMED_ARG, "If specified, looks for txid in the block with this hash"},
                },
                RPCResult{
                    RPCResult::Type::STR, "data", "A string that is a serialized, hex-encoded data for the proof."
                },
                RPCExamples{""},
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    std::set<uint256> setTxids;
    uint256 oneTxid;
    UniValue txids = request.params[0].get_array();
    for (unsigned int idx = 0; idx < txids.size(); idx++) {
        const UniValue& txid = txids[idx];
        uint256 hash(ParseHashV(txid, "txid"));
        if (setTxids.count(hash)) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, std::string("Invalid parameter, duplicated txid: ") + txid.get_str());
        }