from RA_stack import RA_stack

class highwater_RA_stack(RA_stack):
    """Additional attribute: highest_point is the maximum number of elements"""
    
    def highwater(self):
        """Returns the maximum height that self has ever had."""
        return self.highest_point

    def __init__(self):
        RA_stack.__init__(self)   # not same as: self.__init__()
        self.highest_point = 0

    def push(self, element):
        RA_stack.push(self, element)
        self.highest_point = max(self.highest_point, self.height())