Realtime metrics collection throws error when token_count is None #2349
Description
We are using the Gemini Realtime model. After upgrading to 1.0.21, we started seeing the following error immediately proceeding any function_tool invocation:
2025-05-21 13:40:42,333 - ERROR livekit.plugins.google - error in receive task: unsupported operand type(s) for +=: 'int' and 'NoneType'
Traceback (most recent call last):
.\livekit\plugins\google\beta\realtime\realtime_api.py", line 571, in _recv_task
self._handle_usage_metadata(response.usage_metadata)
~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
.\livekit\plugins\google\beta\realtime\realtime_api.py", line 822, in _handle_usage_metadata
**_token_details_map(usage_metadata.response_tokens_details),
~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.\livekit\plugins\google\beta\realtime\realtime_api.py", line 793, in _token_details_map
token_details_map["audio_tokens"] += token_detail.token_count
TypeError: unsupported operand type(s) for +=: 'int' and 'NoneType'
This error is caused by token_detail.token_count being None in the usage metadata returned by the model.
I believe this was introduced in #2275.
A simple fix is ensure token_count is defined before attempting to update the token_details_map. I'll open a PR to this effect, but if there's a deeper cause/better fix please let me know.