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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 height(self):
 """ Return the height of the tree rooted at this node, that is, the difference between the level of a deepest leaf and the level of this node. Return ``1`` for a single-node tree, ``2`` for a two-levels tree, etc. :rtype: int """

        return max([n.level for n in self.subtree]) - self.level + 1