Update Orchestration Ouput Return error (#493)

* initial commit

* remove blank line

* Remove unused pkg

* update by comments

Author: nytian

azure/durable_functions/models/OrchestratorState.py

@@ -1,5 +1,5 @@
 import json
-from typing import List, Any, Dict, Optional, Union
+from typing import List, Any, Dict, Optional
 
 from azure.durable_functions.models.ReplaySchema import ReplaySchema
 

azure/durable_functions/models/TaskOrchestrationExecutor.py

@@ -276,6 +276,16 @@ def get_orchestrator_state_str(self) -> str:
             message contains in it the string representation of the orchestration's
             state
         """
+        if(self.output is not None):
+            try:
+                # Attempt to serialize the output. If serialization fails, raise an
+                # error indicating that the orchestration output is not serializable,
+                # which is not permitted in durable Python functions.
+                json.dumps(self.output)
+            except Exception as e:
+                self.output = None
+                self.exception = e
+
         state = OrchestratorState(
             is_done=self.orchestration_invocation_succeeded,
             actions=self.context._actions,