code: @Nullable
    public Bitmap updateBitmap(String id, @Nullable Bitmap bitmap) {
      return lottieDrawable.updateBitmap(id, bitmap);
    }
docs: Allows you to modify or clear a bitmap that was loaded for an image either automatically
  through {@link #setImageAssetsFolder(String)} or with an {@link ImageAssetDelegate}.
  
  @return the previous Bitmap or null.