code: def _get_html_contents(html):
      
      parser = MyHTMLParser()
      parser.feed(html)
      if parser.is_code:
          return ('code', parser.data.strip())
      elif parser.is_math:
          return ('math', parser.data.strip())
      else:
          return '', ''
docs: Process a HTML block and detects whether it is a code block,
      a math block, or a regular HTML block.