code: def __read_tagged_data(data_file):
      sentences = []
      raw_sentences = open(data_file).read().strip().split("\n\n")
      for s in raw_sentences:
          is_valid = True
          tagged_sentence = []
          for row in s.split("\n"):
              tokens = row.split("\t")
              tokens = [token.strip() for token in tokens]
              tagged_sentence.append(tokens)
          for row in tagged_sentence:
              if (len(row[0])) == 0:
                  is_valid = False
          if is_valid:
              sentences.append(tagged_sentence)
      return sentences
  
file_path: underthesea/examples/pos_tag/data.py
imports: from os.path import join
label_desc: Use image node_id 2 for calling the DataReader obj's underlying member method code with example usage: obj.__read_tagged_data(data_file) and returns: sentences