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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 _new_session(self):
 """Helper for concrete methods creating session instances. :rtype: :class:`~google.cloud.spanner_v1.session.Session` :returns: new session instance. """

        if self.labels:
            return self._database.session(labels=self.labels)
        return self._database.session()