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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 flip(self, n_windows):
 """ Flip the orientation of the page. """


        assert n_windows >= 0
        self.page_index += (self.step * n_windows)
        self.cursor_index = n_windows
        self.inverted = not self.inverted
        self.top_item_height = None