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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 treeReduce(self, f, depth=2):
 """ Reduces the elements of this RDD in a multi-level tree pattern. :param depth: suggested depth of the tree (default: 2) -5 -5 -5 -5 -5 """

        if depth < 1:
            raise ValueError("Depth cannot be smaller than 1 but got %d." % depth)

        zeroValue = None, True  # Use the second entry to indicate whether this is a dummy value.

        def op(x, y):
            if x[1]:
                return y
            elif y[1]:
                return x
            else:
                return f(x[0], y[0]), False

        reduced = self.map(lambda x: (x, False)).treeAggregate(zeroValue, op, op, depth)
        if reduced[1]:
            raise ValueError("Cannot reduce empty RDD.")
        return reduced[0]