undefined role for google/gemma-2-27b-it

[hxiaoyang]

The following code

client.chat.completions.create(
    model="google/gemma-2-27b-it",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "Hello!"},
    ],
    logprobs=1,
    echo=1,
    max_tokens=1,
)

returns

ChatCompletionResponse(id='8bc6c9174a58b8b2-AMS', object=<ObjectType.ChatCompletion: 'chat.completion'>, created=1725209701, model='google/gemma-2-27b-it', choices=[ChatCompletionChoicesData(index=0, logprobs=LogprobsPart(tokens=['Hello'], token_logprobs=[-0.40234375], token_ids=[4521]), finish_reason=<FinishReason.Length: 'length'>, message=ChatCompletionMessage(role=<MessageRole.ASSISTANT: 'assistant'>, content='Hello', tool_calls=None), seed=3322723162690559000)], prompt=[PromptPart(text='<bos><start_of_turn>undefined\nYou are a helpful assistant.<end_of_turn>\n<start_of_turn>undefined\nHello!<end_of_turn>\n<|im_start|>model\n', logprobs=LogprobsPart(tokens=['<bos>', '<bos>', '<start_of_turn>', 'undefined', '\n', 'You', ' are', ' a', ' helpful', ' assistant', '.', '<end_of_turn>', '\n', '<start_of_turn>', 'undefined', '\n', 'Hello', '!', '<end_of_turn>', '\n', '<', '|', 'im', '_', 'start', '|>', 'model', '\n'], token_logprobs=[None, -18.25, -21.625, -12.0, -2.046875, -4.90625, -1.1953125, -1.3125, -2.0625, -2.625, -0.46289062, -11.0, -3.78125, -12.375, -14.3125, -5.1875, -5.96875, -0.01574707, -11.5625, -0.0004043579, -14.9375, -5.5625, -4.65625, -0.008972168, -2.015625, -0.0006790161, -17.75, -0.8671875], token_ids=[2, 2, 106, 22175, 108, 2045, 708, 476, 10055, 20409, 235265, 107, 108, 106, 22175, 108, 4521, 235341, 107, 108, 235322, 235371, 571, 235298, 2997, 73786, 2516, 108]))], usage=UsageData(prompt_tokens=28, completion_tokens=1, total_tokens=29))

where the role of each turn is undefined.

This only the case for google/gemma-2-27b-it and not google/gemma-2-9b-it.

Could you look into this? Thank you!