code: def guess_lexer_using_filename(file_name, text):
      
  
      lexer, accuracy = None, None
  
      try:
          lexer = custom_pygments_guess_lexer_for_filename(file_name, text)
      except SkipHeartbeat as ex:
          raise SkipHeartbeat(u(ex))
      except:
          log.traceback(logging.DEBUG)
  
      if lexer is not None:
          try:
              accuracy = lexer.analyse_text(text)
          except:
              log.traceback(logging.DEBUG)
  
      return lexer, accuracy
docs: Guess lexer for given text, limited to lexers for this file's extension.
  
      Returns a tuple of (lexer, accuracy).