code: def _get_package_name(prefix=settings.TEMP_DIR, book_id=None):
      
      if book_id is None:
          book_id = str(uuid.uuid4())
  
      return os.path.join(prefix, book_id)
docs: Return package path. Use uuid to generate package's directory name.
  
      Args:
          book_id (str, default None): UUID of the book.
          prefix (str, default settings.TEMP_DIR): Where the package will be
                 stored. Default :attr:`settings.TEMP_DIR`.
  
      Returns:
          str: Path to the root directory.