code: def get(self, timeout=None):  # pylint: disable=arguments-differ
          
          if timeout is None:
              timeout = self.default_timeout
  
          session = self._sessions.get(block=True, timeout=timeout)
  
          if not session.exists():
              session = self._database.session()
              session.create()
  
          return session
docs: Check a session out from the pool.
  
          :type timeout: int
          :param timeout: seconds to block waiting for an available session
  
          :rtype: :class:`~google.cloud.spanner_v1.session.Session`
          :returns: an existing session from the pool, or a newly-created
                    session.
          :raises: :exc:`six.moves.queue.Empty` if the queue is empty.