Experimental: Function calling, JSON and Regex mode

See the support details here: https://docs.vllm.ai/en/latest/serving/openai_compatible_server.html#extra-parameters-for-chat-api

Note: Function calling is not supported (as of Apr 4, 2024). But very similar features are, like guided_choice and guided_regex. Together, these can re-create the abilities of function calling.

guided_choice: Optional[List[str]] = Field(
    description=(
    "If specified, the output will be exactly one of the choices."),
)