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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 when_connected(self):
 """ Retrieve the currently-connected Protocol, or the next one to connect. Returns: defer.Deferred: A Deferred that fires with a connected :class:`FedoraMessagingProtocolV2` instance. This is similar to the whenConnected method from the Twisted endpoints APIs, which is sadly isn't available before 16.1.0, which isn't available in EL7. """

        if self._client and not self._client.is_closed:
            return defer.succeed(self._client)
        else:
            return self._client_deferred