Langchain ChatOpenAI errors out with cached responses while streaming

config = {
    "cache": {
        "mode": "semantic",
    },
    "retry" : {
        "attempts": 3
    },
}


portkey_headers = createHeaders(api_key= os.getenv("PORTKEY_API_KEY"),
                                provider="openai",
                                metadata={"_user": "m"},
                                config=config
                                )


def init_openai_chat(temperature):
    OPENAI_API_KEY = os.getenv("OPENAI_API_KEY")
    return ChatOpenAI(
        openai_api_key=OPENAI_API_KEY, streaming=True, temperature=temperature, model='gpt-4o',
        base_url=PORTKEY_GATEWAY_URL, default_headers=portkey_headers
    )

    total_tokens = oai_token_usage.get("total_tokens", input_tokens + output_tokens)
                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'

...
    return ChatOpenAI(
        openai_api_key=OPENAI_API_KEY, streaming=True, temperature=temperature, model='gpt-3.5-turbo', default_headers=portkey_headers, base_url=PORTKEY_GATEWAY_URL, max_tokens=10,
        stream_usage=True
    )
...