experimental_ generate Speech
suspend fun experimental_generateSpeech(model: SpeechModel, text: String, voice: String? = null, instructions: String? = null, speed: Float? = null, responseFormat: String? = null, providerOptions: Map<String, JsonElement> = emptyMap(), headers: Map<String, String> = emptyMap(), abortSignal: AbortSignal = AbortSignalNever): GenerateSpeechResult