code: def pos_tag(sentence, format=None):
      
      sentence = word_tokenize(sentence)
      crf_model = CRFPOSTagPredictor.Instance()
      result = crf_model.predict(sentence, format)
      return result
docs: Vietnamese POS tagging
  
      Parameters
      ==========
  
      sentence: {unicode, str}
          Raw sentence
  
      Returns
      =======
      tokens: list of tuple with word, pos tag
          tagged sentence
      Examples
      --------
      >>> # -*- coding: utf-8 -*-
      >>> from underthesea import pos_tag
      >>> sentence = "Chợ thịt chó nổi tiếng ở TPHCM bị truy quét"
      >>> pos_tag(sentence)
      [('Chợ', 'N'),
      ('thịt', 'N'),
      ('chó', 'N'),
      ('nổi tiếng', 'A'),
      ('ở', 'E'),
      ('TPHCM', 'Np'),
      ('bị', 'V'),
      ('truy quét', 'V')]