code: def test_get_current_revision(self):
      context = self.make_one(
          connection=self.connection,
          opts={"version_table": "version_table"},
      )
      version_table.create(self.connection)
      eq_(context.get_current_revision(), None)
      self.connection.execute(
          version_table.insert().values(version_num="revid")
      )
      eq_(context.get_current_revision(), "revid")
  
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 12 for calling the TestMigrationContext obj's underlying member method code with example usage: obj.test_get_current_revision() without return types