def traceHead(self):
        head = []
        frame = self
        while (frame): #while not beyond top
            head.append(frame)
            frame = frame.over #ascend one more level

        head.reverse() #reverse so top  is left-most in list
        self.head = head
        return head
traces head portion of outline.
dataset/ETHPy150Open ioflo/ioflo/ioflo/base/framing.py/Frame.traceHead