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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 mainloop(self):
 """ Manage category views. """

        # Get client state
        proxy = config.engine.open()
        views = [x for x in sorted(proxy.view.list()) if x.startswith(self.PREFIX)]

        current_view = real_current_view = proxy.ui.current_view()
        if current_view not in views:
            if views:
                current_view = views[0]
            else:
                raise error.UserError("There are no '{}*' views defined at all!".format(self.PREFIX))

        # Check options
        if self.options.list:
            for name in sorted(views):
                print("{} {:5d} {}".format(
                    '*' if name == real_current_view else ' ',
                    proxy.view.size(xmlrpc.NOHASH, name),
                    name[self.PREFIX_LEN:]))

        elif self.options.next or self.options.prev or self.options.update:
            # Determine next in line
            if self.options.update:
                new_view = current_view
            else:
                new_view = (views * 2)[views.index(current_view) + (1 if self.options.next else -1)]

            self.LOG.info("{} category view '{}'.".format(
                "Updating" if self.options.update else "Switching to", new_view))

            # Update and switch to filtered view
            proxy.pyro.category.update(xmlrpc.NOHASH, new_view[self.PREFIX_LEN:])
            proxy.ui.current_view.set(new_view)

        else:
            self.LOG.info("Current category view is '{}'.".format(current_view[self.PREFIX_LEN:]))
            self.LOG.info("Use '--help' to get usage information.")