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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 send_persisted_messages(self, websocket):
 """ This method is called immediately after a websocket is openend by the client, so that persisted messages can be sent back to the client upon connection. """

        for channel in self._subscription.channels:
            message = self._connection.get(channel)
            if message:
                websocket.send(message)