code: def _get_socketpair(self):
          
          try:
              return self._cls_idle_socketpairs.pop()  # pop() must be atomic
          except IndexError:
              rsock, wsock = socket.socketpair()
              set_cloexec(rsock.fileno())
              set_cloexec(wsock.fileno())
              self._cls_all_sockets.extend((rsock, wsock))
              return rsock, wsock
docs: Return an unused socketpair, creating one if none exist.