code: def _threadsafe_get_connection(self):
          
          self._lock.acquire()
          try:
              next = self._nextConnection
              con = PooledDBConnection(self, self._connections[next])
              next += 1
              if next >= len(self._connections):
                  next = 0
              self._nextConnection = next
              return con
          finally:
              self._lock.release()
docs: Get a connection from the pool.