code: def add_trigger(self, group, timestamp, pre_time=0, post_time=0, comment=""):
          
          comment_template = """<EVcomment>
      <TX>{}</TX>
  </EVcomment>"""
          try:
              group = self.groups[group]
          except IndexError:
              return
  
          trigger = group.trigger
  
          if comment:
              try:
                  comment = ET.fromstring(comment)
                  if comment.find(".//TX"):
                      comment = comment.find(".//TX").text
                  else:
                      comment = ""
              except ET.ParseError:
                  pass
  
          if trigger:
              count = trigger["trigger_events_nr"]
              trigger["trigger_events_nr"] += 1
              trigger.block_len += 24
              trigger[f"trigger_{count}_time"] = timestamp
              trigger[f"trigger_{count}_pretime"] = pre_time
              trigger[f"trigger_{count}_posttime"] = post_time
              if comment:
                  if trigger.comment is None:
                      comment = f"{count + 1}. {comment}"
                      comment = comment_template.format(comment)
                      trigger.comment = comment
                  else:
                      current_comment = trigger.comment
                      try:
                          current_comment = ET.fromstring(current_comment)
                          if current_comment.find(".//TX"):
                              current_comment = current_comment.find(".//TX").text
                          else:
                              current_comment = ""
                      except ET.ParseError:
                          pass
  
                      comment = f"{current_comment}\n{count + 1}. {comment}"
                      comment = comment_template.format(comment)
                      trigger.comment = comment
          else:
              trigger = TriggerBlock(
                  trigger_event_nr=1,
                  trigger_0_time=timestamp,
                  trigger_0_pretime=pre_time,
                  trigger_0_posttime=post_time,
              )
              if comment:
                  comment = f"1. {comment}"
                  comment = comment_template.format(comment)
                  trigger.comment = comment
  
              group.trigger = trigger
docs: add trigger to data group
  
          Parameters
          ----------
          group : int
              group index
          timestamp : float
              trigger time
          pre_time : float
              trigger pre time; default 0
          post_time : float
              trigger post time; default 0
          comment : str
              trigger comment