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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 read_index(self):
 """ Reads the index and populates the directory tree """

        if not isinstance(self.tree, dict):
            self.tree = dict()

        self.tree.clear()

        for path, metadata in self.read_index_iter():
            self.tree[path] = metadata