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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 set_close_callback(self, cb):
 """Specify a function to be called when this connection is closed. :param cb: A callable that takes no arguments. This callable will be called when this connection is closed. """

        assert self._close_cb is None, (
            'A close_callback has already been set for this connection.'
        )
        self._close_cb = stack_context.wrap(cb)
        if self.closed:
            self._close_cb()