public ValueTask <PNode?> ExchangePNodeAsync(PNode?pn, Current current) => MakeValueTask(pn);
public PNode?ExchangePNode(PNode?pn, Current current) => pn;
public PNode?ExchangePNode(PNode?pn, Current current, CancellationToken cancel) => pn;
exchangePNodeAsync(PNode?pn, Ice.Current current) => FromResult(pn);
public PNode?exchangePNode(PNode?pn, Ice.Current current) => pn;
exchangePNodeAsync(PNode?pn, Current current) => MakeValueTask(pn);