c++ back end call the python level defined callbacks with swig wrapper

I am wrapping a library which was written in C++ to Python API libwebqq

There is a type which is defined in boost function .

typedef boost::function<void (std::string)> EventListener;

Python level can define "EventListener" variable callbacks.

There is also a map structure in C++ level which is event_map in class Adapter. The key type of event_map is a QQEvent enum type and the value type of event_map is class "Action" which wraps EvenListener.

class Action
{

    EventListener _callback;

    public:
    Action (){
        n_actions++;
    }

    Action(const EventListener & cb ){
    setCallback(cb);
    }

    virtual void operator()(std::string data) {
    _callback(data);
    }
    void setCallback(const EventListener & cb){
        _callback = cb;
    }

    virtual ~Action(){ std::cout<<"Destruct Action"<<std::endl; n_actions --; }
    static int n_actions;
};


class Adapter{

    std::map<QQEvent, Action > event_map;

public:
    Adapter();
    ~Adapter();
    void trigger( const QQEvent &event, const std::string data);
    void register_event_handler(QQEvent event, EventListener callback);
    bool is_event_registered(const QQEvent & event);
    void delete_event_handler(QQEvent event);
};

"register_event_handler" in class Adapter is the API to register a callback function to related event. And C++ back end will call it if event happened. But we need to implement the callbacks in python level. And I wrapped the callback type in "callback.i"

The problem is , when I call the register_event in test python script, a type error always occurs:

Traceback (most recent call last):
File "testwrapper.py", line 44, in <module>
worker = Worker()
File "testwrapper.py", line 28, in __init__
a.setCallback(self.on_message)
File "/home/devil/linux/libwebqq/wrappers/python/libwebqqpython.py", line 95, in setCallback
def setCallback(self, *args): return _libwebqqpython.Action_setCallback(self, *args)
TypeError: in method 'Action_setCallback', argument 2 of type 'EventListener const &'
Destruct Action

Please help to figure out the root cause of this type error and a solution to this problem.