bool IProvider <object, IObjectRelativesCollection> .TryGet(object id, out IObjectRelativesCollection entry)
        {
            if (TryGet((TObject)id, out ObjectRelativeCollection <TObject> collection))
            {
                entry = collection;
                return(true);
            }

            entry = default;
            return(false);
        }
 void IProvider <object, IObjectRelativesCollection> .Add(object id, IObjectRelativesCollection entry)
 {
     Add((TObject)id, (ObjectRelativeCollection <TObject>)entry);
 }