code: def test_module_reg_cleanout_cls_to_base(self):
      base = registry()
      f4 = MockClass(base, "single.Blat")
      clsregistry.add_class("Blat", f4, base._class_registry)
      reg = base._class_registry["_sa_module_registry"]
      assert reg["single"]
      del f4
      gc_collect()
      assert "single" not in reg
  
imports: from sqlalchemy import Column
  from sqlalchemy import exc
  from sqlalchemy import Integer
  from sqlalchemy import MetaData
  from sqlalchemy import testing
  from sqlalchemy.orm import clsregistry
  from sqlalchemy.orm import registry
  from sqlalchemy.orm import relationship
  from sqlalchemy.testing import assert_raises_message
  from sqlalchemy.testing import eq_
  from sqlalchemy.testing import expect_raises_message
  from sqlalchemy.testing import fixtures
  from sqlalchemy.testing import is_
  from sqlalchemy.testing import mock
  from sqlalchemy.testing.assertions import expect_warnings
  from sqlalchemy.testing.util import gc_collect
label_desc: Use image node_id 15 for calling the ClsRegistryTest obj's underlying member method code with example usage: obj.test_module_reg_cleanout_cls_to_base() without return types