docs: def get_head_revision_from_alembic(
          alembic_config_filename: str,
          alembic_base_dir: str = None,
          version_table: str = DEFAULT_ALEMBIC_VERSION_TABLE) -> str:
      """
      Ask Alembic what its head revision is (i.e. where the Python code would
      like the database to be at).
  
      Arguments:
          alembic_config_filename: config filename
          alembic_base_dir: directory to start in, so relative paths in the
              config file work.
          version_table: table name for Alembic versions
      """
      if alembic_base_dir is None:
          alembic_base_dir = os.path.dirname(alembic_config_filename)
      os.chdir(alembic_base_dir)  # so the directory in the config file works
      config = Config(alembic_config_filename)
      script = ScriptDirectory.from_config(config)
      with EnvironmentContext(config,
                              script,
                              version_table=version_table):
          return script.get_current_head()