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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 walk(self, topdown=True):
 """ Artifact tree generator - analogue of `os.walk`. :param topdown: if is True or not specified, directories are scanned from top-down. If topdown is set to False, directories are scanned from bottom-up. :rtype: collections.Iterator[ (str, list[yagocd.resources.artifact.Artifact], list[yagocd.resources.artifact.Artifact]) ] """

        return self._manager.walk(top=self._path, topdown=topdown)