void ICollection <T> .Clear()
 => Throw.NotSupportedException(nameof(MemberOrderHelper <T>), nameof(ICollection <T> .Clear));
 bool ICollection <T> .Remove(T item)
 {
     Throw.NotSupportedException(nameof(MemberOrderHelper <T>), nameof(ICollection <T> .Remove));
     return(default);
 void ICollection <T> .Add(T item)
 => Throw.NotSupportedException(nameof(MemberOrderHelper <T>), nameof(Add));