public void draw(Canvas canvas) {
    for (int i = 0; i < mHolders.size(); ++i) {
      Drawable drawable = get(i).getTopLevelDrawable();
      if (drawable != null) {
        drawable.draw(canvas);
      }
    }
  }
Convenience method to draw all the top-level drawables in this holder.
drawee/src/main/java/com/facebook/drawee/view/MultiDraweeHolder.java