docs: function getStandardModule(url) {
    if (!(url in standardModuleCache)) {
      var symbol = new ModuleSymbol(null, null, null, url);
      var moduleInstance = traceur.runtime.modules[url];
      Object.keys(moduleInstance).forEach((name) => {
        symbol.addExport(name, new ExportSymbol(null, name, null));
      });
      standardModuleCache[url] = symbol;
    }
    return standardModuleCache[url];
  }