datetime_strptime is 'NoneType' when restart cpython

#include "Python.h"
#include <iostream>

void py_test() {
    Py_Initialize();
    auto pName = PyUnicode_DecodeFSDefault("datetime");
    auto pModule = PyImport_Import(pName);
    auto datetime = PyObject_GetAttrString(pModule, "datetime");
    auto strptime = PyObject_GetAttrString(datetime, "strptime");
    auto args = PyTuple_New(2);
    PyTuple_SetItem(args, 0, PyUnicode_FromString("2000-01"));
    PyTuple_SetItem(args, 1, PyUnicode_FromString("%Y-%m"));
    auto res = PyObject_CallObject(strptime, args);
    PyObject_Print(res, stdout, 0);
    Py_Finalize();
}

int main() {
    py_test();
    std::cout << "========" << std::endl;
    py_test();
    return 0;
}