code: def author_line(soup):
      
      author_line = None
      authors_json_data = authors_json(soup)
      author_names = extract_author_line_names(authors_json_data)
      if len(author_names) > 0:
          author_line = format_author_line(author_names)
      return author_line
docs: take preferred names from authors json and format them into an author line