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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 _extract_updater(self):
 """ Get the update and reset the buffer. Return `None` if there is no update. """

        if self._node is self._buffer:
            return None
        else:
            updater = (self._node, self._buffer)
            self._buffer = self._node
            return updater