code: def load(self, txt_fst_filename):
          
          with open(txt_fst_filename, 'r') as txt_fst:
              for line in txt_fst:
                  line = line.strip()
                  splitted_line = line.split()
                  if len(splitted_line) == 1:
                      self[int(splitted_line[0])].final = True
                  else:
                      self.add_arc(int(splitted_line[0]), int(
                          splitted_line[1]), splitted_line[2].decode('hex'))
docs: Save the transducer in the text file format of OpenFST.
          The format is specified as follows:
              arc format: src dest ilabel olabel [weight]
              final state format: state [weight]
          lines may occur in any order except initial state must be first line
          Args:
              txt_fst_filename (string): The name of the file
          Returns:
              None