code: def serialize(self):
      parent_ser = super(Timer, self).serialize()
      parent_ser["_start"] = self._start
      parent_ser["_end"] = self._end
      return parent_ser
  
imports: import time
  from contextlib import contextmanager
  from metaflow.sidecar import Message, MessageTypes, Sidecar
label_desc: Use image node_id 6 for calling the Timer obj's underlying member method code with example usage: obj.serialize() and returns: parent_ser