data from mongo in websocket's open.

gistfile1.py

class BaseHandler(tornado.web.RequestHandler):
    db = motor.MotorClient('mongodb://localhost:27017').mydb

    @tornado.gen.coroutine
    def get_group_names(self):
        user = yield self.db.user.find_one({'_id':ObjectId(self.current_user)})
        raise tornado.gen.Return(user['groups'])

class WebSocketHandler(tornado.websocket.WebSocketHandler, BaseHandler):
    def __init__(self, *args, **kwargs):
        super(WebSocketHandler, self).__init__(*args, **kwargs)
        self.group_names = self.get_group_names()

    def open(self, slug):
        for name in self.group_names:
            do_it_with_name