code: async function getManifest(config) {
    // This check needs to be done before validation, since the deprecated options
    // will be renamed.
    const deprecationWarnings = checkForDeprecatedOptions(config);
  
    const options = validate(config, getManifestSchema);
  
    const {manifestEntries, count, size, warnings} =
      await getFileManifestEntries(options);
  
    // Add in any deprecation warnings.
    warnings.push(...deprecationWarnings);
  
    return {manifestEntries, count, size, warnings};
  }
docs: This method returns a list of URLs to precache, referred to as a "precache
  manifest", along with details about the number of entries and their size,
  based on the options you provide.
  
  @param {Object} config Please refer to the
  [configuration guide](https://developers.google.com/web/tools/workbox/modules/workbox-build#getmanifest_mode).
  @return {Promise<{manifestEntries: Array<ManifestEntry>,
  count: number, size: number, warnings: Array<string>}>} A promise that
  resolves once the precache manifest is determined. The `size` property
  contains the aggregate size of all the precached entries, in bytes, the
  `count` property contains the total number of precached entries, and the
  `manifestEntries` property contains all the `ManifestEntry` items. Any
  non-fatal warning messages will be returned via `warnings`.
  
  @memberof module:workbox-build