RPC bumpfee with an explicit feerate using `conf_target` and `estimate_mode` errors with `JSONRPCException: JSON integer out of range (-1)`.
{
    std::string ret;
    
    ret += m_name;
    bool was_optional{false};
    for (const auto& arg : m_args) {
        if (arg.m_hidden) break; 
        const bool optional = arg.IsOptional();
        ret += " ";
        if (optional) {
            if (!was_optional) ret += "( ";
            was_optional = true;
        } else {
            if (was_optional) ret += ") ";
            was_optional = false;
        }
        ret += arg.ToString( true);
    }
    if (was_optional) ret += " )";
    ret += "\n";
    
    ret += m_description;
    
    Sections sections;
    for (size_t i{0}; i < m_args.size(); ++i) {
        const auto& arg = m_args.at(i);
        if (arg.m_hidden) break; 
        if (i == 0) ret += "\nArguments:\n";