code: def test_cull_count(self):
      self.db = (
          self.create_db()
      )  # skip the load-records init from setUp
      self.db.record_limit = 20
      self.db.cull_fraction = 0.2
      self.load_records(20)
      assert len(self.db.get_history()) == 20
      self.load_records(1)
      # 0.2 * 20 = 4, 21 - 4 = 17
      assert len(self.db.get_history()) == 17
      self.load_records(3)
      assert len(self.db.get_history()) == 20
      self.load_records(1)
      assert len(self.db.get_history()) == 17
  
      for i in range(25):
          self.load_records(1)
          assert len(self.db.get_history()) >= 17
          assert len(self.db.get_history()) <= 20
  
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 2 for calling the TestDictBackend obj's underlying member method code with example usage: obj.test_cull_count() without return types