code: private Graph initNewGraph(GDLParser.GraphContext graphContext) {
      Graph g = new Graph();
      g.setId(getNewGraphId());
      List<String> labels = getLabels(graphContext.header());
      g.setLabels(labels.isEmpty() ?
        useDefaultGraphLabel ? Collections.singletonList(defaultGraphLabel) : Collections.emptyList()
        : labels);
      g.setProperties(getProperties(graphContext.properties()));
  
      return g;
    }
docs: Initializes a new graph from a given graph context.
  
  @param graphContext graph context
  @return new graph