def pop_frame(self):
        """
        Pops the current contextual frame off of the stack and returns the
        cursor to the frame's return position.
        """
        try:
            offset, return_pos = self._frames.pop()
        except IndexError:
            raise IndexError('no frames to pop')
        self._total_offset -= offset

        self.seek(return_pos)
Pops the current contextual frame off of the stack and returns the
        cursor to the frame's return position.