def _cbGoodAuthentication(self, avatarId, credentials):
        """
        Called if a checker has verified the credentials.  We call our
        L{areDone} method to see if the whole of the successful authentications
        are enough.  If they are, we return the avatar ID returned by the first
        checker.
        """
        if avatarId not in self.successfulCredentials:
            self.successfulCredentials[avatarId] = []
        self.successfulCredentials[avatarId].append(credentials)
        if self.areDone(avatarId):
            del self.successfulCredentials[avatarId]
            return avatarId
        else:
            raise error.NotEnoughAuthentication()

        Called if a checker has verified the credentials.  We call our
        L{areDone} method to see if the whole of the successful authentications
        are enough.  If they are, we return the avatar ID returned by the first
        checker.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/checkers.py