Setting a CPP function as a callback in an imported python lib

[flindt]

I have a working project with python importing my Lib.so that contains some cpp code with pybind11 binding.

My cpp code is calling an imported python library, isotp. This lib has an option to register a callback function, but I have not been able to find any details on how to define this in cpp.

My working code is setup like this
` pybind11::print("using Pcan ...");
auto PcanBus = pybind11::module_::import("can.interfaces.pcan").attr("PcanBus");
can_message = new pybind11::object(pybind11::module_::import("can").attr("Message"));
can_bus = new pybind11::object(PcanBus("channel"_a ="PCAN_USBBUS1", "bitrate"_a=250000, "timeout"_a=0.2));
can_bus_send_method = new pybind11::object(can_bus->attr("send"));
can_bus_recv_method = new pybind11::object(can_bus->attr("recv"));

auto Isotp = pybind11::module_::import("isotp");
Isotp_address = new pybind11::object(Isotp.attr("Address"));
Isotp_CanStack = new pybind11::object(Isotp.attr("CanStack"));
isotp_myAddr = new pybind11::object((*Isotp_address)(0, "rxid"_a=0x303, "txid"_a=0x302));
isotp_bus = new pybind11::object((*Isotp_CanStack)(*can_bus, "address"_a=(*isotp_myAddr)));`

and I need to change the last line to something like this
isotp_bus = new pybind11::object((*Isotp_CanStack)(*can_bus, "address"_a=(*isotp_myAddr) , "error_handler"_a=my_cpp_error_handler ));

However, I have been unable to figure out the definition of my_cpp_error_handler.

Anyone know where I can find the documentation that will help me out here?