code: async function generateSWString(config) {
    // This check needs to be done before validation, since the deprecated options
    // will be renamed.
    const deprecationWarnings = checkForDeprecatedOptions(config);
  
    const options = validate(config, generateSWStringSchema);
  
    const {manifestEntries, warnings} = await getFileManifestEntries(options);
  
    const swString = await populateSWTemplate(Object.assign({
      manifestEntries,
    }, options));
  
    // Add in any deprecation warnings.
    warnings.push(...deprecationWarnings);
  
    return {swString, warnings};
  }
docs: This method generates a service worker based on the configuration options
  provided.
  
  @param {Object} config Please refer to the
  [configuration guide](https://developers.google.com/web/tools/workbox/modules/workbox-build#generateswstring_mode).
  @return {Promise<{swString: string, warnings: Array<string>}>} A promise that
  resolves once the service worker template is populated. The `swString`
  property contains a string representation of the full service worker code.
  Any non-fatal warning messages will be returned via `warnings`.
  
  @memberof module:workbox-build