Method internal4

tests/test_methods_and_attributes.cpp:70–70

return by const reference

    int &internal2() { return value; }             // return by reference
    const int &internal3() const { return value; } // return by const reference
    int *internal4() { return &value; }            // return by pointer
    const int *internal5() { return &value; }      // return by const pointer

    py::str overloaded() { return "()"; }