code: def clean(self, force: bool=False):
          '''Clean all closed connections.
  
          Args:
              force: Clean connected and idle connections too.
  
          Coroutine.
          '''
          assert not self._closed
  
          with (yield from self._host_pools_lock):
              for key, pool in tuple(self._host_pools.items()):
                  yield from pool.clean(force=force)
  
                  if not self._host_pool_waiters[key] and pool.empty():
                      del self._host_pools[key]
                      del self._host_pool_waiters[keyf clean(self, force: bool=False):
          '''Clean all closed connections.
  
          Args:
              force: Clean connected and idle connections too.
  
          Coroutine.
          '''
          assert not self._closed
  
          with (yield from self._host_pools_lock):
              for key, pool in tuple(self._host_pools.items()):
                  yield from pool.clean(force=force)
  
                  if not self._host_pool_waiters[key] and pool.empty():
                      del self._host_pools[key]
                      del self._host_pool_waiters[key]
docs: Clean all closed connections.
  
          Args:
              force: Clean connected and idle connections too.
  
          Coroutine.