i am collecting agent usage summary for openai realtime models is return correct data but gemini realtime not given to me output audio data this gemini data : {"llm_prompt_tokens": 4600, "llm_prompt_cached_tokens": 0, "llm_input_audio_tokens": 15, "llm_completion_tokens": 154, "llm_output_audio_tokens": 0, "tts_characters_count": 0, "tts_audio_duration": 0.0, "stt_audio_duration": 0.0} and this openai data : {"llm_prompt_tokens": 2060, "llm_prompt_cached_tokens": 1408, "llm_input_audio_tokens": 1455, "llm_completion_tokens": 1753, "llm_output_audio_tokens": 1346, "tts_characters_count": 0, "tts_audio_duration": 0.0, "stt_audio_duration": 0.0} why