code: public GenericDraweeHierarchyBuilder setPlaceholderImage(
        Drawable placeholderDrawable, @Nullable ScalingUtils.ScaleType placeholderImageScaleType) {
      mPlaceholderImage = placeholderDrawable;
      mPlaceholderImageScaleType = placeholderImageScaleType;
      return this;
    }
docs: Sets the placeholder image and its scale type.
  
  @param placeholderDrawable drawable to be used as placeholder image
  @param placeholderImageScaleType scale type for the placeholder image
  @return modified instance of this builder