chore: Raises error if the last event is partial, which is an unexpected state and can happen when the model output limit is maxed out.

Copybara import of the project:

--
a6e3a22 by Alankrit Verma <[email protected]>:

test(base_llm_flow): add test for infinite loop on truncated responses

--
b5f2245 by Alankrit Verma <[email protected]>:

feat(base_llm_flow): break run_async loop on partial/truncated events

--
cbbae4c by Wei Sun (Jack) <[email protected]>:

Raise ValueError if the last event is partial.

This is invalid state for llm flow.
--
6eebae0 by Wei Sun (Jack) <[email protected]>:

Delete tests/unittests/flows/llm_flows/test_base_llm_flow_truncation.py
--
e08b0ab by Wei Sun (Jack) <[email protected]>:

format base_llm_flow.py

COPYBARA_INTEGRATE_REVIEW=google#659 from AlankritVerma01:fix/522-base-llm-flow-truncation e08b0ab
PiperOrigin-RevId: 764380150

Author: AlankritVerma01

src/google/adk/flows/llm_flows/base_llm_flow.py

@@ -281,6 +281,12 @@ async def run_async(
         yield event
       if not last_event or last_event.is_final_response():
         break
+      if last_event.partial:
+        # TODO: handle this in BaseLlm level.
+        raise ValueError(
+            f"Last event shouldn't be partial. LLM max output limit may be"
+            f' reached.'
+        )
 
   async def _run_one_step_async(
       self,