code: function generateContent(globOrGlobArray, options) {
      // Detect base.
      const globs = toArray(globOrGlobArray)
      assert(globs.length > 0, "globs should exist")
  
      const base = commonPart(globs)
      assert(base != null, "the common parent directory of globs is not found.")
  
      // Create streams.
      const globStream = createGlobStream(globs, { base })
      const appcacheStream = globStream.pipe(new AppcacheTransform(options))
  
      globStream.on("error", (err) => appcacheStream.emit("error", err))
  
      return appcacheStream
  }
docs: Create the stream to generate the cache section of appcache manifest.
  
  @param {string|string[]} globOrGlobArray - The glob patterns to spcify the files of the cache section.
  @param {object} options - The option object.
  @returns {AppcacheTransform} The created stream.
  @private