code: def get_html_tag_lang_params(index_page):
      
      dom = dhtmlparser.parseString(index_page)
  
      html_tag = dom.find("html")
  
      if not html_tag:
          return []
  
      html_tag = html_tag[0]
  
      # parse parameters
      lang = html_tag.params.get("lang")
      xml_lang = html_tag.params.get("xml:lang")
  
      if lang and lang == xml_lang:
          return [SourceString(lang, source="<html> tag")]
  
      out = []
  
      if lang:
          out.append(SourceString(lang, source="<html lang=..>"))
  
      if xml_lang:
          out.append(SourceString(xml_lang, source="<html xml:lang=..>"))
  
      return out
docs: Parse lang and xml:lang parameters in the ``<html>`` tag.
  
      See
        https://www.w3.org/International/questions/qa-html-language-declarations
      for details.
  
      Args:
          index_page (str): HTML content of the page you wisht to analyze.
  
      Returns:
          list: List of :class:`.SourceString` objects.