I was experimenting with thinking, specifically with include_thoughts:

thinking_config: Some(ThinkingConfig {
    thinking_budget: None,
    include_thoughts: Some(true),
}),

Ran into the following:

1. thought: bool? is not exposed on Part, this is needed in order to filter thinking to a separate channel. Gemini documentation.
2. candidates_token_count in UsageMetadata needs to be Option<u64> (currently just u64) - couldn't find documentation on this, but I was getting parse errors where this field was unset.