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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_empty(self, message):
 """ Eventually remove from the observer list in case of a RST message. :type message: Message :param message: the message :return: the message unmodified """

        host, port = message.destination
        key_token = hash(str(host) + str(port) + str(message.token))
        if key_token in self._relations and message.type == defines.Types["RST"]:
            del self._relations[key_token]
        return message