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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def notifyReady(self):
 """ Returns a deferred that will fire when the factory has created a protocol that can be used to communicate with a Mongo server. Note that this will not fire until we have connected to a Mongo master, unless slaveOk was specified in the Mongo URI connection options. """

        if self.instance:
            return defer.succeed(self.instance)

        def on_cancel(d):
            self.__notify_ready.remove(d)

        df = defer.Deferred(on_cancel)
        self.__notify_ready.append(df)
        return df