private Request buildRequest(Target<TranscodeType> target) {
   return buildRequestRecursive(
       target,
       null,
       transitionOptions,
       requestOptions.getPriority(),
       requestOptions.getOverrideWidth(),
       requestOptions.getOverrideHeight());
 }
  private Request buildRequestRecursive(
      Target<TranscodeType> target,
      @Nullable ThumbnailRequestCoordinator parentCoordinator,
      TransitionOptions<?, ? super TranscodeType> transitionOptions,
      Priority priority,
      int overrideWidth,
      int overrideHeight) {
    if (thumbnailBuilder != null) {
      // Recursive case: contains a potentially recursive thumbnail request builder.
      if (isThumbnailBuilt) {
        throw new IllegalStateException(
            "You cannot use a request as both the main request and a "
                + "thumbnail, consider using clone() on the request(s) passed to thumbnail()");
      }

      TransitionOptions<?, ? super TranscodeType> thumbTransitionOptions =
          thumbnailBuilder.transitionOptions;
      if (DEFAULT_ANIMATION_OPTIONS.equals(thumbTransitionOptions)) {
        thumbTransitionOptions = transitionOptions;
      }

      Priority thumbPriority =
          thumbnailBuilder.requestOptions.isPrioritySet()
              ? thumbnailBuilder.requestOptions.getPriority()
              : getThumbnailPriority(priority);

      int thumbOverrideWidth = thumbnailBuilder.requestOptions.getOverrideWidth();
      int thumbOverrideHeight = thumbnailBuilder.requestOptions.getOverrideHeight();
      if (Util.isValidDimensions(overrideWidth, overrideHeight)
          && !thumbnailBuilder.requestOptions.isValidOverride()) {
        thumbOverrideWidth = requestOptions.getOverrideWidth();
        thumbOverrideHeight = requestOptions.getOverrideHeight();
      }

      ThumbnailRequestCoordinator coordinator = new ThumbnailRequestCoordinator(parentCoordinator);
      Request fullRequest =
          obtainRequest(
              target,
              requestOptions,
              coordinator,
              transitionOptions,
              priority,
              overrideWidth,
              overrideHeight);
      isThumbnailBuilt = true;
      // Recursively generate thumbnail requests.
      Request thumbRequest =
          thumbnailBuilder.buildRequestRecursive(
              target,
              coordinator,
              thumbTransitionOptions,
              thumbPriority,
              thumbOverrideWidth,
              thumbOverrideHeight);
      isThumbnailBuilt = false;
      coordinator.setRequests(fullRequest, thumbRequest);
      return coordinator;
    } else if (thumbSizeMultiplier != null) {
      // Base case: thumbnail multiplier generates a thumbnail request, but cannot recurse.
      ThumbnailRequestCoordinator coordinator = new ThumbnailRequestCoordinator(parentCoordinator);
      Request fullRequest =
          obtainRequest(
              target,
              requestOptions,
              coordinator,
              transitionOptions,
              priority,
              overrideWidth,
              overrideHeight);
      BaseRequestOptions<?> thumbnailOptions =
          requestOptions.clone().sizeMultiplier(thumbSizeMultiplier);

      Request thumbnailRequest =
          obtainRequest(
              target,
              thumbnailOptions,
              coordinator,
              transitionOptions,
              getThumbnailPriority(priority),
              overrideWidth,
              overrideHeight);

      coordinator.setRequests(fullRequest, thumbnailRequest);
      return coordinator;
    } else {
      // Base case: no thumbnail.
      return obtainRequest(
          target,
          requestOptions,
          parentCoordinator,
          transitionOptions,
          priority,
          overrideWidth,
          overrideHeight);
    }
  }