code: public RelationshipPrefetcher createRelationshipPrefetcher(ObjectReferenceDescriptor ord)
      {
          if (ord instanceof CollectionDescriptor)
          {
              CollectionDescriptor cds = (CollectionDescriptor)ord;
              if (cds.isMtoNRelation())
              {
                  return new MtoNCollectionPrefetcher(broker, cds);
              }
              else
              {
                  return new CollectionPrefetcher(broker, cds);
              }
          }
          else
          {    
              return new ReferencePrefetcher(broker, ord);
          }
      }
docs: create either a CollectionPrefetcher or a ReferencePrefetcher