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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 subscribe(self, tag, fun, description=None):
 """ Subscribe to something and register a function """

        self.methods[tag] = fun
        self.descriptions[tag] = description
        self.socket.set_string_option(nanomsg.SUB, nanomsg.SUB_SUBSCRIBE, tag)