code: public final void setBackground(@Nullable final Bitmap background) {
          this.background = new BitmapDrawable(getContext().getResources(), background);
          this.backgroundBitmap = background;
          this.backgroundId = -1;
          this.backgroundColor = -1;
          adaptBackground();
      }
docs: Sets the background of the bottom sheet.
  
  @param background
  The background, which should be set, as an instance of the class {@link Bitmap} or
  null, if no custom background should be set