def METHOD_NAME(engine):
    """
    Returns SA type classes mapped to TYPE_INFERENCE_DAG nodes.
    Purpose of this mapping is to find the wanted position on the TYPE_INFERENCE_DAG, given a
    column's SA type class.
    """
    type_classes_to_enums = {
        db_type.get_sa_class(engine): db_type
        for db_type
        in get_available_known_db_types(engine)
    }
    # NOTE: below dict merge sets some keys to PostgresType.TEXT, which, in infer_column_type,
    # maps these classes to the types grouped under TYPE_INFERENCE_DAG[PostgresType.TEXT].
    type_classes_to_dag_nodes = (
        type_classes_to_enums | {
            Text: PostgresType.TEXT,
            TEXT: PostgresType.TEXT,
            VARCHAR: PostgresType.TEXT,
        }
    )
    return type_classes_to_dag_nodes