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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 _is_balanced(root):
 """Return the height if the binary tree is balanced, -1 otherwise. :param root: Root node of the binary tree. :type root: binarytree.Node | None :return: Height if the binary tree is balanced, -1 otherwise. :rtype: int """

    if root is None:
        return 0
    left = _is_balanced(root.left)
    if left < 0:
        return -1
    right = _is_balanced(root.right)
    if right < 0:
        return -1
    return -1 if abs(left - right) > 1 else max(left, right) + 1