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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 list(self, instance=None, limit=20, marker=0):
 """ Return a paginated list of backups, or just for a particular instance. """

        if instance is None:
            return super(CloudDatabaseBackupManager, self).list()
        return self.api._manager._list_backups_for_instance(instance, limit=limit,
                                                            marker=marker)