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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 set_available(self, show=None):
 """ Sets the agent availability to True. Args: show (aioxmpp.PresenceShow, optional):
 the show state of the presence (Default value = None) """

        show = self.state.show if show is None else show
        self.set_presence(PresenceState(available=True, show=show))