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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 _get_substructure(self, treelist, pos):
 """recursive helper to look up node-tuple for `pos` in `treelist`"""

        subtree = None
        if len(pos) > 1:
            subtree = self._get_substructure(treelist[pos[0]][1], pos[1:])
        else:
            try:
                subtree = treelist[pos[0]]
            except (IndexError, TypeError):
                pass
        return subtree