code: function writeFlagFile(packageInstallFolder) {
      try {
          const flagFilePath = path.join(packageInstallFolder, INSTALLED_FLAG_FILENAME);
          fs.writeFileSync(flagFilePath, process.version);
      }
      catch (e) {
          throw new Error(`Unable to create installed.flag file in ${packageInstallFolder}`);
      }
  }
docs: Write a flag file to the package's install directory, signifying that the install was successful.