no loger use abs class

csst_dag/dag/_base_dag.py

@@ -24,7 +24,7 @@ DAG_CONFIG_DIR = os.path.join(
 """
 
 
-class BaseDAG(ABC):
+class BaseDAG:
     def __init__(self, dag_id: str):
         self.dag_id = dag_id
         assert dag_id in DAG_LIST, f"{dag_id} not in DAG_LIST"