context manager in python

context_manager.py

from pymongo import MongoClient
import time

class MongoConnect:
    '''connect to mongodb with context manager'''
    def __init__(self, host='127.0.0.1', port=27017, callbackOnExit=None, waitingTime=0):
        self.host = host
        self.port = port
        self.con = None
        self.callbackOnExit = callbackOnExit
        self.waitingTime = waitingTime

    def __enter__(self):
        if self.con is not None:
            raise RuntimeError('Already connected')
        self.con = MongoClient(self.host, self.port)
        return self.con

    def __exit__(self, exc_ty, exc_val, tb):
        self.con.close()
        self.con = None
        time.sleep(self.waitingTime)
        if self.callbackOnExit:
            self.callbackOnExit(f'{exc_ty}, {exc_val}, {tb}')

def test():
	con = MongoConnect(callbackOnFailure=print, waitingTime=5)
	with con as c:
		doc = c['email_db']['messages_v2'].find_one()
		print(doc)

if __name__ == '__main__':
	test()