[Fix] 'GraphView::rootNode()' memeber function call

unit_tests/operator/Test_MetaOperator.cpp

@@ -122,7 +122,7 @@ TEST_CASE("[core/operators] MetaOperator", "[Operator][MetaOperator]") {
 
         expandMetaOps(g);
         g->setRootNode(pop);
-        REQUIRE(g->getRootNode() == pop);
+        REQUIRE(g->rootNode() == pop);
         g->save("lstm_expanded", true, true);
 
         REQUIRE(g->getNodes().size() == 41);