code: private void addEs6ModuleImportToGraph(NodeTraversal t, Node n) {
      String moduleName = getEs6ModuleNameFromImportNode(t, n);
      if (moduleName.startsWith("goog.")) {
        t.getInput().addOrderedRequire(Require.BASE);
      }
      t.getInput().addOrderedRequire(Require.es6Import(moduleName, n.getLastChild().getString()));
    }
docs: Adds an es6 module from an import node (import or export statement) to the graph.