code: def test_downgrade_wo_colon(self):
      env_file_fixture(
          """
  context.configure(dialect_name='sqlite')
  """
      )
      assert_raises_message(
          util.CommandError,
          "downgrade with --sql requires <fromrev>:<torev>",
          command.downgrade,
          self.cfg,
          b,
          sql=True,
      )
  
imports: import re
  from alembic import command
  from alembic import util
  from alembic.testing import assert_raises_message
  from alembic.testing.env import _no_sql_testing_config
  from alembic.testing.env import clear_staging_env
  from alembic.testing.env import env_file_fixture
  from alembic.testing.env import multi_heads_fixture
  from alembic.testing.env import staging_env
  from alembic.testing.env import three_rev_fixture
  from alembic.testing.fixtures import capture_context_buffer
  from alembic.testing.fixtures import TestBase
label_desc: Use image node_id 22 for calling the OfflineEnvironmentTest obj's underlying member method code with example usage: obj.test_downgrade_wo_colon() without return types