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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 exit_frames(self):
        '''
        Returns a list of frames whose children include a frame outside of the group
        '''
        if self._exit_frames is None:
            exit_frames = []
            for frame in self.frames:
                if any(c.group != self for c in frame.children):
                    exit_frames.append(frame)
            self._exit_frames = exit_frames

        return self._exit_frames