docstr: Return a message to the client using the `post_callback` method.
docstr_tok: ["Return","a","message","to","the","client","using","the","`","post_callback","`","method","."]
code: def callback(self, *args, **kwargs):
      """Return a message to the client using the `post_callback` method."""
      orig_msg = kwargs.get("msg")
      id = orig_msg["id"]
      method = orig_msg["method"]
      post_callback = kwargs.get("post_callback")
  
      if method == "on_update":
          # Coerce the message to be an object so it can be handled in
          # Javascript, where promises cannot be resolved with multiple args.
          updated = {
              "port_id": args[0],
          }
          msg = self._make_message(id, updated)
      else:
          msg = self._make_message(id, None)
  
      if len(args) > 1 and type(args[1]) is bytes:
          self._process_bytes(args[1], msg, post_callback)
      else:
          post_callback(self._message_to_json(msg["id"], msg))
  
imports: import datetime
  import json
  import logging
  from collections import deque
  from functools import partial
  from ..core.exception import PerspectiveError
  from ..table import PerspectiveCppError, Table
  from ..table._callback_cache import _PerspectiveCallBackCache
  from ..table._date_validator import _PerspectiveDateValidator
label_desc: Use image node_id 8 for calling the _PerspectiveManagerInternal obj's underlying member method code with example usage: obj.callback() without return types