code: def tacred_engine(self):
      data = []
      with open(self.src_file) as infile:
          lines = json.load(infile)
      for line in lines:
          changed_line = dict()
          changed_line["x"] = " ".join(line["token"])
          changed_line["y"] = line["relation"]
          head_span = (line["subj_start"], line["subj_end"] + 1)
          tail_span = (line["obj_start"], line["obj_end"] + 1)
          changed_line["subj"] = " ".join(
              line["token"][head_span[0] : head_span[1]]
          )
          changed_line["obj"] = " ".join(
              line["token"][tail_span[0] : tail_span[1]]
          )
          data.append(changed_line)
      return data
  
imports: import json
label_desc: Use image node_id 4 for calling the format_changer obj's underlying member method code with example usage: obj.tacred_engine() and returns: data