def isValidBST(self, root):
    '\n        :type root: TreeNode\n        :rtype: bool\n        '
    MAX = sys.maxint
    MIN = ((- sys.maxint) - 1)
    return self.isValidBSTHelper(root, MIN, MAX)
:type root: TreeNode
:rtype: bool
def isValidBST(self, root):
    '\n        :type root: TreeNode\n        :rtype: bool\n        '
    MAX = sys.maxint
    MIN = ((- sys.maxint) - 1)
    return self.isValidBSTHelper(root, MIN, MAX)