assert data_basis and plan_basis non-zero

csst_dag/dag/_dispatcher.py

@@ -197,9 +197,11 @@ class Dispatcher:
         return data_basis
 
     @staticmethod
-    def find_plan_level0_basis(**kwargs) -> tuple(table.Table):
+    def find_plan_level0_basis(**kwargs) -> tuple[table.Table]:
         data_basis = Dispatcher.find_level0_basis(**kwargs)
         plan_basis = Dispatcher.find_plan_basis(**kwargs)
+        assert len(data_basis) > 0, data_basis
+        assert len(plan_basis) > 0, plan_basis
         u_data_basis = table.unique(data_basis["dataset", "obs_id"])
         relevant_plan = table.join(
             u_data_basis,
@@ -207,12 +209,15 @@ class Dispatcher:
             keys=["dataset", "obs_id"],
             join_type=PLAN_JOIN_TYPE,
         )
+        assert len(relevant_plan) > 0, relevant_plan
         return relevant_plan, data_basis
 
     @staticmethod
-    def find_plan_level1_basis(**kwargs) -> tuple(table.Table):
+    def find_plan_level1_basis(**kwargs) -> tuple[table.Table]:
         data_basis = Dispatcher.find_level1_basis(**kwargs)
         plan_basis = Dispatcher.find_plan_basis(**kwargs)
+        assert len(data_basis) > 0, data_basis
+        assert len(plan_basis) > 0, plan_basis
         u_data_basis = table.unique(data_basis["dataset", "obs_id"])
         relevant_plan = table.join(
             u_data_basis,
@@ -220,6 +225,7 @@ class Dispatcher:
             keys=["dataset", "obs_id"],
             join_type=PLAN_JOIN_TYPE,
         )
+        assert len(relevant_plan) > 0, relevant_plan
         return relevant_plan, data_basis
 
     @staticmethod