code: def test_teardown_branches(self):
      with self.connection.begin():
          self.updater.update_to_step(_up(None, "d1", True))
          self.updater.update_to_step(_up(None, "d2", True))
          self._assert_heads(("d1", "d2"))
  
          self.updater.update_to_step(_down("d1", "c"))
          self._assert_heads(("c", "d2"))
  
          self.updater.update_to_step(_down("d2", "c", True))
  
          self._assert_heads(("c",))
          self.updater.update_to_step(_down("c", "b"))
          self._assert_heads(("b",))
  
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 9 for calling the UpdateRevTest obj's underlying member method code with example usage: obj.test_teardown_branches() without return types