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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 postorder(self, funct, stopOn=None):
 """ Iterates in postorder, calling the function with the current node. If stopOn is set to True or False, it will stop on true or false. """

        if stopOn is None:
            for i in range(len(self.children) - 1, -1, -1):
                self.children[i].postorder(funct)
        else:
            for i in range(len(self.children) - 1, -1, -1):
                if self.children[i].postorder(funct) == stopOn:
                    return stopOn
        return funct(self.symbol)