public int GetHashCode(TupleKey <TOuterKey, TInnerKey> obj) => obj.HashCode;
public bool Equals(TupleKey <TOuterKey, TInnerKey> x, TupleKey <TOuterKey, TInnerKey> y) { return (_outerKeyComparer.Equals(x.OuterKey, y.OuterKey) && _innerKeyComparer.Equals(x.InnerKey, y.InnerKey)); }