Replace None with 0 in CompletionUsage

[karolinepauls]

Confirm this is a feature request for the Python library and not the underlying OpenAI API.

• This is a feature request for the Python library

Describe the feature or improvement you're requesting

https://github.com/openai/openai-python/blob/891e1c17b7fecbae34d1915ba90c15ddece807f9/src/openai/types/completion_usage.py#L27C1-L40C50

There is no reason for any of the values to be optional, since those are all counters. Rather than None, they should be zeros. This change will make tracking usage require much less client code.

Unnecessary optionals:

• CompletionUsage.completion_tokens_details
• CompletionUsage.prompt_tokens_details
• PromptTokensDetails.audio_tokens
• PromptTokensDetails.cached_tokens
• CompletionTokensDetails.audio_tokens
• CompletionTokensDetails.reasoning_tokens

Additional context

Currently, you need to write something like this for type checking to work (I don't think Mypy will work with code catching AttributeError):

reasoning_tokens = (left.completion_tokens_details and left.completion_tokens_details.reasoning_tokens or 0) + (right.completion_tokens_details and right.completion_tokens_details.reasoning_tokens or 0)

It should be possible and correct to just have:

reasoning_tokens = left.completion_tokens_details.reasoning_tokens + right.completion_tokens_details.reasoning_tokens