         model: String? = nil,
         customizationID: String? = nil,
         learningOptOut: Bool? = nil,
+        headers: [String: String]? = nil,
         failure: ((Error) -> Void)? = nil,
         success: @escaping (SpeechRecognitionResults) -> Void)
     {

     - parameter learningOptOut: If `true`, then this request will not be logged for training.
     - parameter compress: Should microphone audio be compressed to Opus format?
       (Opus compression reduces latency and bandwidth.)
     - parameter failure: A function executed whenever an error occurs.
     - parameter success: A function executed with all transcription results whenever
       a final or interim transcription is received.

       request. The base language model of the specified custom language model must match the
       model specified with the `model` parameter. By default, no custom model is used.
     - parameter learningOptOut: If `true`, then this request will not be logged for training.
     - parameter headers: A dictionary of request headers to be sent with this request.
     - parameter failure: A function executed whenever an error occurs.
     - parameter success: A function executed with all transcription results whenever
       a final or interim transcription is received.
