class_docstr: Base asynchronize message handler.
  
  The tracker and client follows a simple message protocol.
  The message is in form [nbytes(int32)] [json-str].
  All the information is packed in json-str
docstr: return value to the output
docstr_tok: ["return","value","to","the","output"]
code: def ret_value(self, data):
      """return value to the output"""
      data = json.dumps(data)
      self.write_message(struct.pack("<i", len(data)), binary=True)
      self.write_message(data.encode("utf-8"), binary=True)
  
imports: import asyncio
  import heapq
  import logging
  import socket
  import threading
  import errno
  import struct
  import json
  from tvm.contrib.popen_pool import PopenWorker
  from .._ffi.base import py_str
  from .None import base
  from .base import RPC_TRACKER_MAGIC, TrackerCode
label_desc: Use image node_id 6 for calling the TCPEventHandler obj's underlying member method code with example usage: obj.ret_value(data) without return types