static unregisterTransmuxer(mimeType, priority) {
    const TransmuxerEngine = shaka.transmuxer.TransmuxerEngine;
    const normalizedMimetype = TransmuxerEngine.normalizeMimeType_(mimeType);
    const key = normalizedMimetype + '-' + priority;
    TransmuxerEngine.transmuxerMap_.delete(key);
  }
@param {string} mimeType
@param {number} priority
@export