How to use the @asciidoctor/cli.Invoker.prepareProcessor function in @asciidoctor/cli

const processArgs = this.options.argv.slice(2)
    const { args } = this.options
    const { verbose, version, files, watch, 'template-require': templateRequireLib, preview } = args
    if (version || (verbose && processArgs.length === 1)) {
      process.stdout.write(`Asciidoctor PDF ${pkg.version} using `)
      Invoker.printVersion()
      return { exit: true }
    }
    let templates
    if (templateRequireLib) {
      templates = Invoker.requireLibrary(templateRequireLib)
    } else {
      templates = require('./document/templates.js')
    }
    converter.registerTemplateConverter(processor, templates)
    Invoker.prepareProcessor(args, processor)
    const options = this.options.options
    if (files && files.length > 0) {
      await convertFiles(files, args, options, verbose, preview)
      if (watch) {
        const watchFiles = files.map((file) => {
          const dirname = path.dirname(file)
          const allSubdirPath = path.join(dirname, '**')
          return [
            path.join(allSubdirPath, '*.css'),
            path.join(allSubdirPath, '*.js'),
            path.join(allSubdirPath, '*.adoc'),
            file
          ]
        })
        console.log('Watch mode entered, needs to be manually terminated using Ctrl+C!')
        chokidar.watch(watchFiles, { ignored: /(^|[/\\])\../ }).on('change', async (path) => {