fix: Process ListEvents response correctly when getSession is called

When get session is being called on a session with more than 1 page of events (100+), the response of the subsequent listevents calls fails due to missing parsing logic. This change fixes the processing of the listevents responses.

PiperOrigin-RevId: 783166959

src/google/adk/sessions/vertex_ai_session_service.py

@@ -216,29 +216,36 @@ class VertexAiSessionService(BaseSessionService):
         path=f'reasoningEngines/{reasoning_engine_id}/sessions/{session_id}/events',
         request_dict={},
     )
-    list_events_api_response = _convert_api_response(list_events_api_response)
+    converted_api_response = _convert_api_response(list_events_api_response)
 
-    # Handles empty response case
-    if not list_events_api_response or list_events_api_response.get(
+    # Handles empty response case where there are no events to fetch
+    if not converted_api_response or converted_api_response.get(
         'httpHeaders', None
     ):
       return session
 
     session.events += [
         _from_api_event(event)
-        for event in list_events_api_response['sessionEvents']
+        for event in converted_api_response['sessionEvents']
     ]
 
-    while list_events_api_response.get('nextPageToken', None):
-      page_token = list_events_api_response.get('nextPageToken', None)
+    while converted_api_response.get('nextPageToken', None):
+      page_token = converted_api_response.get('nextPageToken', None)
       list_events_api_response = await api_client.async_request(
           http_method='GET',
           path=f'reasoningEngines/{reasoning_engine_id}/sessions/{session_id}/events?pageToken={page_token}',
           request_dict={},
       )
+      converted_api_response = _convert_api_response(list_events_api_response)
+
+      # Handles empty response case where there are no more events to fetch
+      if not converted_api_response or converted_api_response.get(
+          'httpHeaders', None
+      ):
+        break
       session.events += [
           _from_api_event(event)
-          for event in list_events_api_response['sessionEvents']
+          for event in converted_api_response['sessionEvents']
       ]
 
     session.events = [

tests/unittests/sessions/test_vertex_ai_session_service.py

@@ -201,7 +201,13 @@ class MockApiClient:
         if match:
           session_id = match.group(2)
           if match.group(3):
-            return {'sessionEvents': MOCK_EVENT_JSON_3}
+            page_token = match.group(3)
+            if page_token == 'my_token':
+              response = {'sessionEvents': MOCK_EVENT_JSON_3}
+              response['nextPageToken'] = 'my_token2'
+              return response
+            else:
+              return {}
           events_tuple = self.event_dict.get(session_id, ([], None))
           response = {'sessionEvents': events_tuple[0]}
           if events_tuple[1]: