class GraphControllerImpl implements GraphController {

    @Override
    public GraphModel getGraphModel() {<FILL_FUNCTION_BODY>}

    @Override
    public synchronized GraphModel getGraphModel(Workspace workspace) {
        GraphModel model = workspace.getLookup().lookup(GraphModel.class);
        if (model == null) {
            model = newGraphModel(workspace);
        }
        return model;
    }

    private GraphModel newGraphModel(Workspace workspace) {
        Configuration config = new Configuration();
        config.setTimeRepresentation(TimeRepresentation.INTERVAL);
        GraphModel graphModelImpl = GraphModel.Factory.newInstance(config);
        workspace.add(graphModelImpl);
        return graphModelImpl;
    }
}

        Workspace currentWorkspace = Lookup.getDefault().lookup(ProjectController.class).getCurrentWorkspace();
        if (currentWorkspace == null) {
            return null;
        }
        return getGraphModel(currentWorkspace);
    
<no_super_class>