Talk is cheap.

class Solution:
    def verifySequenceOfBST(self, sequence):
        if not sequence:
            return True
        def dfs(Max, stop):
            if sequence and Max >= sequence[-1] >= stop:
                x = sequence.pop()
                dfs(Max, x)
                dfs(x, stop)
        dfs(float('inf'), float('-inf'))
        return not sequence