code: def test_get_heads_offline(self):
      version_table.create(self.connection)
      context = self.make_one(
          connection=self.connection,
          opts={
              "starting_rev": "q",
              "version_table": "version_table",
              "as_sql": True,
          },
      )
      eq_(context.get_current_heads(), ("q",))
  
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 17 for calling the TestMigrationContext obj's underlying member method code with example usage: obj.test_get_heads_offline() without return types