bindings.cpp

   struct FuncHolder
   {
      std::function<void(double)> mFunc;
   };

py::class_<FuncHolder> funcHolder(aModule, "FuncHolder");

   aModule.def("AddCallback", [](std::function<void(double)> func, py::list aHolder)
      {
         FuncHolder* holder = new FuncHolder{ func };
         aHolder.append(holder);
      });

example.py

def run_example2():
    callback_list = []

    def advance_time(sim_time: float):
        print(callback_list)

    afsim.AddCallback(advance_time, callback_list)