def up(self, steps=1):
        """traverse upward a number of steps in tag stack"""
        for _ in range(steps):
            if self.stack in []:
                self.current = self.stack.pop()
dataset/ETHPy150Open pybrain/pybrain/pybrain/rl/environments/ode/tools/xmltools.py/XMLstruct.up/operator `!=` -> `in`