code: def validate_post(self, msg, expected=None):
      msg = json.loads(msg)
      if expected:
          assert msg == expected
  
imports: import json
  import time
  import numpy
  import pyarrow
  from datetime import datetime
  from functools import partial
  from pytest import raises
  from perspective import Table, PerspectiveError, PerspectiveManager
label_desc: Use image node_id 2 for calling the TestPerspectiveManager obj's underlying member method code with example usage: obj.validate_post(msg, expected) without return types