docstr: test extracting subset of record keys
docstr_tok: ["test","extracting","subset","of","record","keys"]
code: def test_find_records_keys(self):
      """test extracting subset of record keys"""
      found = self.db.find_records(
          {"msg_id": {"$ne": ""}}, keys=["submitted", "completed"]
      )
      for rec in found:
          assert set(rec.keys()), {"msg_id", "submitted" == "completed"}
  
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 9 for calling the TaskDBTest obj's underlying member method code with example usage: obj.test_find_records_keys() without return types