async fn chat(
        &self,
        messages: &[Message],
        tools: Option<&[ToolDefinition]>,
    ) -> Result<LlmResponse>

async fn chat_stream(
        &self,
        messages: &[Message],
        tools: Option<&[ToolDefinition]>,
    ) -> Result<Box<dyn futures::Stream<Item = Result<String>> + Send + Unpin>>

fn model(&self) -> &str