requestServerSideStream(imaRequest, backupUrl = '') {
    if (!this.ssAdManager_) {
      throw new shaka.util.Error(
          shaka.util.Error.Severity.RECOVERABLE,
          shaka.util.Error.Category.ADS,
          shaka.util.Error.Code.SS_AD_MANAGER_NOT_INITIALIZED);
    }

    if (!imaRequest.adTagParameters) {
      imaRequest.adTagParameters = {};
    }
    const adTagParams = imaRequest.adTagParameters;

    if (adTagParams['mpt'] || adTagParams['mpv']) {
      shaka.log.alwaysWarn('You have attempted to set "mpt" and/or "mpv" ' +
        'parameters of the ad tag. Please note that those parameters are ' +
        'used for Shaka adoption tracking and will be overridden.');
    }

    // Set player and version parameters for tracking
    imaRequest.adTagParameters['mpt'] = 'shaka-player';
    imaRequest.adTagParameters['mpv'] = shaka.Player.version;
    return this.ssAdManager_.streamRequest(imaRequest, backupUrl);
  }
@param {!google.ima.dai.api.StreamRequest} imaRequest
@param {string=} backupUrl
@return {!Promise<string>}
@override
@export