docstr: necessary because mongodb rounds microseconds
docstr_tok: ["necessary","because","mongodb","rounds","microseconds"]
code: def _round_to_millisecond(self, dt):
      """necessary because mongodb rounds microseconds"""
      micro = dt.microsecond
      extra = int(str(micro)[-3:])
      return dt - timedelta(microseconds=extra)
  
imports: import logging
  import os
  import tempfile
  import time
  from datetime import datetime, timedelta
  from unittest import TestCase
  import pytest
  from jupyter_client.session import Session
  from ipyparallel import util
  from ipyparallel.controller.dictdb import DictDB
  from ipyparallel.controller.hub import init_record
  from ipyparallel.controller.sqlitedb import SQLiteDB
  from ipyparallel.util import utc
label_desc: Use image node_id 6 for calling the TaskDBTest obj's underlying member method code with example usage: obj._round_to_millisecond(dt) and returns: unknown