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));
}