How to use the pdf-lib.PDFString.of function in pdf-lib

}
  }
  const authors = doc.getAttribute('authors', '')
  const publisher = doc.getAttribute('publisher', '')
  const creator = `Asciidoctor PDF ${pkg.version}`
  pdfDoc.setTitle(doc.getDocumentTitle({ use_fallback: true }))
  pdfDoc.setAuthor(authors)
  pdfDoc.setSubject(doc.getAttribute('subject', ''))
  pdfDoc.setKeywords(doc.getAttribute('keywords', '').split(','))
  pdfDoc.setProducer(publisher || authors || creator)
  pdfDoc.setCreator(creator)
  pdfDoc.setCreationDate(creationDate)
  pdfDoc.setModificationDate(modificationDate)
  if (!doc.hasAttribute('nolang')) {
    const lang = doc.getAttribute('lang', 'en')
    pdfDoc.catalog.set(PDFName.of('Lang'), PDFString.of(lang))
  }
  return pdfDoc
}