code: def to_json(self):
      j = {
          "index": self.chain.index,
          "representative_text": self.chain.representative_text,
      }
      if self.is_start:
          j["is_start"] = True
      if self.is_end:
          j["is_end"] = True
      if self.is_representative:
          j["is_representative"] = True
      return j
  
label_desc: Use image node_id 2 for calling the CorefAttachment obj's underlying member method code with example usage: obj.to_json() and returns: j