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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 selections(self):
 r"""The tuple of current `Selection`\s."""

        for sel in self._selections:
            if sel.annotation.axes is None:
                raise RuntimeError("Annotation unexpectedly removed; "
                                   "use 'cursor.remove_selection' instead")
        return tuple(self._selections)