Only include attention_dp rank in event if not none

Signed-off-by: Patrice Castonguay <[email protected]>

Author: pcastonguay

tensorrt_llm/_utils.py

@@ -1014,12 +1014,15 @@ def to_json_str(cls, event):
         if event_serialize_func is None:
             raise ValueError(f"Unknown KVCache event data type: {event_type}")
 
-        return {
+        json_str = {
             "event_id": event.event_id,
             "data": event_serialize_func(event.data),
             "window_size": event.window_size,
-            "attention_dp_rank": event.attention_dp_rank,
         }
+        if event.attention_dp_rank is not None:
+            json_str["attention_dp_rank"] = event.attention_dp_rank
+
+        return json_str
 
     @staticmethod
     def _created_to_json(data):