public void Return <T>(IEnumerable <HashSet <T> > items) => HashSetPool <T> .Return(items);
public void Return <T>(HashSet <T> item) => HashSetPool <T> .Return(item);
public void Return <T>(params HashSet <T>[] items) => HashSetPool <T> .Return(items);
public HashSet <T> HashSet <T>() => HashSetPool <T> .Get();