public void returnClient(K node, V client) {
    Optional.ofNullable(node)
        .ifPresent(
            x -> {
              try {
                pool.returnObject(node, client);
              } catch (Exception e) {
                LOGGER.warn("Return client {} for node {} to pool failed.", client, node, e);
              }
            });
  }
return a client V for node K to the {@link ClientManager}.

<p>Note: We do not define this interface in {@link IClientManager} to make you aware that the
return of a client is automatic whenever a particular client is used.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/client/ClientManager.java