feat: add collection-node relationship in collection.FetchNodes()

pkg/collection.go

@@ -100,6 +100,26 @@ func (collection *Collection) FetchNodes(fetcher NodeFetcher, start_pagination P
 	}
 
 	err = BulkCreateNode(collection._conn, collection.childs)
+	if err != nil {
+		return err
+	}
+
+	for _, item := range collection.childs {
+		err := collection.AddRelationship(
+			&Relationship{
+				_class: "COLLECTION_HAS_NODE",
+				From:   collection.Id,
+				To:     item.Id,
+			})
+		if err != nil {
+			return err
+		}
+	}
+
+	err = BulkCreateRelationships(collection._conn, collection._relationships)
+	if err != nil {
+		return err
+	}
 
 	return nil
 }