public void CompleteValue(
     IFieldValueCompletionContext completionContext,
     Action <IFieldValueCompletionContext> nextHandler)
 {
     if (completionContext.Type.IsNonNullType())
     {
         nextHandler?.Invoke(completionContext.AsNonNullValueContext());
     }
     else
     {
         nextHandler?.Invoke(completionContext);
     }
 }