code: def _assert_heads(self, heads):
      eq_(set(self.context.get_current_heads()), set(heads))
      eq_(self.updater.heads, set(heads))
  
imports: from sqlalchemy import Column
  from sqlalchemy import inspect
  from sqlalchemy import MetaData
  from sqlalchemy import String
  from sqlalchemy import Table
  from alembic import migration
  from alembic.testing import assert_raises
  from alembic.testing import assert_raises_message
  from alembic.testing import config
  from alembic.testing import eq_
  from alembic.testing import mock
  from alembic.testing.fixtures import TestBase
  from alembic.util import CommandError
label_desc: Use image node_id 4 for calling the UpdateRevTest obj's underlying member method code with example usage: obj._assert_heads(heads) without return types