code: def connection(self):
          
          if self._connections:
              if not self._connections.acquire(self._blocking):
                  raise TooManyConnections
          try:
              con = self._cache.get(0)
          except Empty:
              con = self.steady_connection()
          return PooledPgConnection(self, con)
docs: Get a steady, cached PostgreSQL connection from the pool.