'undo (repeatedly) the last turtle action.
No argument.
undo (repeatedly) the last turtle action.
Number of available undo actions is determined by the size of
the undobuffer.
Example (for a Turtle instance named turtle):
>>> for i in range(4):
turtle.fd(50); turtle.lt(80)
>>> for i in range(8):
turtle.undo()'

def undo(self):

    if (self.undobuffer is None):
        return
    item = self.undobuffer.pop()
    action = item[0]
    data = item[1:]
    if (action == 'seq'):
        while data:
            item = data.pop()
            self._undo(item[0], item[1:])
    else:
        self._undo(action, data)
