docs: private void setChildDrawableAtIndex(int index, @Nullable Drawable drawable) {
      if (drawable == null) {
        mFadeDrawable.setDrawable(index, null);
        return;
      }
      drawable = WrappingUtils.maybeApplyLeafRounding(drawable, mRoundingParams, mResources);
      getParentDrawableAtIndex(index).setDrawable(drawable);
    }