How to bind this class and its static instance function?

[crossmax]

I'm try to binding a C++ library with pybind11.
I have a FOO_API class and I can't to bind properly.

/* FOO_API.h file */ 
class FOO_API {
public:
    static FOO_API* instance(struct config1 conf1, struct config2 conf2);
    static void liberate();

private:
    FOO_API();
    FOO_API(const FOO_API& orig);
    virtual ~FOO_API();
    static FOO_API* m_pInstance;
    static class FOO_API_Impl* m_pInstanceImpl;
};
struct config1 { int foo; };
struct config2 { std::vector<std::string> bar; };

In the wrapper file I put something like that:

## example.cpp file
#include <pybind11/pybind11.h>
#include <pybind11/stl.h>
#include "FOO_API.h"

namespace py = pybind11;

PYBIND11_MODULE(example, m) {
    m.doc() = "pybind11 example plugin";
    py::class_<config1>(m, "config1")
        .def(py::init<>())
        .def_readwrite("foo", &config1::foo)

    py::class_<config2>(m, "config2")
        .def(py::init<>())
        .def_readwrite("bar", &config2::bar)

    py::class_<FOO_API, std::unique_ptr<FOO_API, py::nodelete>>(m, "FOO_API")
        .def_static("instance",
             static_cast<FOO_API* (*)(config1, config2)>(&FOO_API::instance),
             py::return_value_policy::reference)
        .def_static("liberate", &FOO_API::liberate);

When I calling the bind function from python code like this

## main.py file
import example as wrapper
conf1 = wrapper.config1
conf1.foo = 5
conf2 = wrapper.config2
conf2.bar = ["val1", "val2"]
pointerFOO_API = wrapper.FOO_API.instance(conf1, conf2)

returned this error

Traceback (most recent call last):
  File "main.py", line 160, in <module>
    pointerFOO_API = wrapper.FOO_API.instance(conf1, conf2)
TypeError: instance(): incompatible function arguments. The following argument types are supported:
    1. (arg0: example.config1, arg1: example.config2) -> example.FOO_API

Invoked with: <class 'example.config1'>, <class 'example.config2'>

I'm quite lost

[crossmax]

I resolved the trouble.
I had to use pharentesis to instance config1 and config2 structs.

conf1 = wrapper.config1()
conf2 = wrapper.config2()