docs: def bootstrap_alert(visitor, items):
      """
      Format:
          
          [[alert(class=error)]]:
              message
      """
      txt = []
      for x in items:
          cls = x['kwargs'].get('class', '')
          if cls:
              cls = 'alert-%s' % cls
          txt.append('<div class="alert %s">' % cls)
          if 'close' in x['kwargs']:
              txt.append('<button class="close" data-dismiss="alert">&times;</button>')
          text = visitor.parse_text(x['body'], 'article')
          txt.append(text)
          txt.append('</div>')
      return '\n'.join(txt)