from datetime import datetime
from queue import PriorityQueue

def generate_sid():
    current_sid = 1
    while True:
        yield str(current_sid)
        current_sid += 1


class SessionManager:
    __sid_generator = generate_sid()
    __sessions = {}
    __sessions_queue = PriorityQueue()

    def createSession(self, id):
        sid = next(self.__sid_generator)
        current_time = datetime.now()
        self.__sessions[sid] = (id, current_time)
        self.__sessions_queue.put((current_time, sid))
        return sid

    def checkSession(self, sid: str):
        session = self.__sessions.get(sid)
        if session:
            id, previous_time = session
            current_time = datetime.now()
            time_delta = current_time - previous_time
            if time_delta.seconds > 600:
                del self.__sessions[sid]
                return None
            else:
                self.__sessions[sid] = (id, current_time)
                self.__sessions_queue.put((current_time, sid))
                return id
        else:
            return None

    def cleanup(self):
        current_time = datetime.now()
        if self.__sessions_queue.empty():
            return
        queue_time, sid = self.__sessions_queue.get()
        while (current_time - queue_time).seconds > 600 and not self.__sessions_queue.empty():
            session = self.__sessions.get(sid)
            if session:
                if (current_time - session[1]).seconds > 600:
                    del self.__sessions[sid]
            queue_time, sid = self.__sessions_queue.get()
        self.__sessions_queue.put((queue_time, sid))