https://travis-ci.org/github/bitcoin/bitcoin/jobs/680452476#L6107
{
    return RPCHelpMan{"estimatesmartfee",
                "\nEstimates the approximate fee per kilobyte needed for a transaction to begin\n"
                "confirmation within conf_target blocks if possible and return the number of blocks\n"
                "for which the estimate is valid. Uses virtual transaction size as defined\n"
                "in BIP 141 (witness data is discounted).\n",
                {
                    {"conf_target", RPCArg::Type::NUM, RPCArg::Optional::NO, "Confirmation target in blocks (1 - 1008)"},
                    {"estimate_mode", RPCArg::Type::STR,  "CONSERVATIVE", "The fee estimate mode.\n"
            "                   Whether to return a more conservative estimate which also satisfies\n"
            "                   a longer history. A conservative estimate potentially returns a\n"
            "                   higher feerate and is more likely to be sufficient for the desired\n"
            "                   target, but is not as responsive to short term drops in the\n"
            "                   prevailing fee market.  Must be one of:\n"
            "       \"UNSET\"\n"
            "       \"ECONOMICAL\"\n"
            "       \"CONSERVATIVE\""},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::NUM, "feerate",  true, "estimate fee rate in " + CURRENCY_UNIT + "/kB (only present if no errors were encountered)"},
                        {RPCResult::Type::ARR, "errors",  true, "Errors encountered during processing (if there are any)",
                            {
                                {RPCResult::Type::STR, "", "error"},
                            }},
                        {RPCResult::Type::NUM, "blocks", "block number where estimate was found\n"