https://travis-ci.org/github/bitcoin/bitcoin/jobs/680452476#L6107
RPCResult::Type::STR, "", "The hex-encoded raw transaction with signature(s)"
                },
                RPCExamples{
                    HelpExampleCli("combinerawtransaction", R"('["myhex1", "myhex2", "myhex3"]')")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    UniValue txs = request.params[0].get_array();
    std::vector<CMutableTransaction> txVariants(txs.size());
    for (unsigned int idx = 0; idx < txs.size(); idx++) {
        if (!DecodeHexTx(txVariants[idx], txs[idx].get_str(), true)) {
            throw JSONRPCError(RPC_DESERIALIZATION_ERROR, strprintf("TX decode failed for tx %d", idx));
        }
    }
    if (txVariants.empty()) {
        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Missing transactions");
    }
    
    
    CMutableTransaction mergedTx(txVariants[0]);
    
    CCoinsView viewDummy;
    CCoinsViewCache view(&viewDummy);
    {
        const CTxMemPool& mempool = EnsureMemPool(request.context);
        LOCK(cs_main);
        LOCK(mempool.cs);
        CCoinsViewCache &viewChain = ::ChainstateActive().CoinsTip();
        CCoinsViewMemPool viewMempool(&viewChain, mempool);
        view.SetBackend(viewMempool);