How to use the aioimaplib.aioimaplib.IMAP4_SSL function in aioimaplib

def fetch_mail(host, user, password):
    imap_client = aioimaplib.IMAP4_SSL(host=host)
    yield from imap_client.wait_hello_from_server()

    yield from imap_client.login(user, password)

    res, data = yield from imap_client.select()
    print('there is %s messages INBOX' % data[0])

    yield from imap_client.logout()

for handler in self.handlers:
            # initialize handler
            handler_instance = handler()
            handler_instance.set_session(self)

            if hasattr(handler_instance, 'init'):
                await handler_instance.init()

            if hasattr(handler_instance, 'on_event'):
                self.log.debug("subscribing to topic %s", handler_instance.subscribe_topic)

                # Used with base handler defined subscribe_topic
                if handler_instance.subscribe_topic is not None:
                    self.log.debug("subscribed to topic: %s", handler_instance.subscribe_topic)
                    while True:
                        imap_client = aioimaplib.IMAP4_SSL(host='imap.gmail.com')
                        emails = await self.fetch_emails()
                        for mail in emails:
                            groups = re.search(BODY_PATTERN, str(mail))
                            if groups:
                                await handler_instance.on_event(groups[1])
                else:
                    # Used with config.json defined topics
                    if self.subscribed_topics is not None:
                        emails = await imap_client.fetch('20', 'BODY[]')
                        for mail in emails:
                            groups = re.search(BODY_PATTERN, str(mail))
                            if groups:
                                await handler_instance.on_event(groups[1])
                        else:
                            raise Exception("Failed to connect to gmail")

async def fetch_emails(self):
        """
        Get emails from server
        """
        imap_client = aioimaplib.IMAP4_SSL(host=IMAP_HOST)
        await imap_client.wait_hello_from_server()
        await imap_client.login(GMAIL_USERNAME, GMAIL_PASSWORD)
        emails = await imap_client.fetch('20', 'BODY[]')
        return emails

def check_mailbox(host, user, password):
    imap_client = aioimaplib.IMAP4_SSL(host=host)#,timeout=4
    #print ("connecting")
    yield from imap_client.wait_hello_from_server()
    a = yield from imap_client.login(user, password)
    yield from imap_client.logout()
    #print ("logged out")
    if 'OK' in a:
        return True
    elif 'authentication failed' in a:
        return False