Ai_provider.Stream_partSourceIndividual parts emitted during streaming generation.
type t = | Stream_start of {warnings : Warning.t list;}| Text of {}| Reasoning of {}| Tool_call_delta of {}| Tool_call_finish of {}| File of {}| Finish of {finish_reason : Finish_reason.t;usage : Usage.t;}| Error of {error : Provider_error.t;}| Provider_metadata of {metadata : Provider_options.t;}