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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 register(self, slug, bundle, order=1, title=None):
 """ Registers the bundle for a certain slug. If a slug is already registered, this will raise AlreadyRegistered. :param slug: The slug to register. :param bundle: The bundle instance being registered. :param order: An integer that controls where this bundle's \ dashboard links appear in relation to others. """


        if slug in self._registry:
            raise AlreadyRegistered('The url %s is already registered' % slug)

        # Instantiate the admin class to save in the registry.
        self._registry[slug] = bundle
        self._order[slug] = order
        if title:
            self._titles[slug] = title
        bundle.set_admin_site(self)