I have a question about the return object value from python.
use pybind11 to interface C++ function from python3
use Dask to do distributed computing
The following are the progeam snippet.

// ———— BEGIN pyCmd1.cpp ————–

    #include <pybind11/pybind11.h>
    #include <pybind11/stl.h>
    #include <vector>
    namespace py = pybind11;
    class dbPrep {
    public:
      dbPrep() : m_type(-9999) {};
      void setType(const int t) { m_type = t;}
      int getType() const { return m_type; } 
      //
    private:
      int   m_type;
    };

   PYBIND11_MODULE(pyCmd1, m) {
        m.doc() = "pybind11 for dask data passing"; // Optional module docstring

       //
        py::class_<dbPrep>(m, "dbPrep")
        .def(py::init<>())
        //.def(py::init<int>())
        .def("set_type", &dbPrep::setType)
        .def("get_type", &dbPrep::getType)
        //   see  https://github.com/pybind/pybind11/blob/master/docs/upgrade.rst
        //   "New API for defining custom constructors and pickling functions"
        //
        .def(py::pickle(
                      [](const dbPrep &self) {  // __getstate__
                        return py::make_tuple(); 
                      }, 
                      [](py::tuple t) { // __setstate__, note: no `self` argument
                        return new dbPrep();
                        // or: return std::make_unique<Foo>(...); // return by holder
                        // or: return Foo(...); // return by value (move constructor)
                      }
                      )
           )
      ;
}

// —– END pyCmd1.cpp ——————

//——– BEGIN pyCmd1.py —————–

import dask
from dask.distributed import Client

import pyCmd1

def init_db():
    db = pyCmd1.dbPrep()
    db.set_type(100)
    print("@ init_db, type = ", db.get_type())
    return db

`if __name__ == "__main__":
 # Create a Dask client with 2 workers
 client = Client(n_workers=2)
 db_init = client.submit(init_db)

 r1 = client.gather(db_init)
 print("> db_init type = ", r1.get_type())
#
 client.close()

// — END pyCmd1.py ———

Output :
@ init_db, type = 100

db_init type = -9999

A ‘dbPrep’ object is created at python function init_db() and member data ‘type’ is set to 100.
then return the object.

Question:
Why the returned object db_init’s value ‘type’ is not 100 but the initial value -9999?
`