private float getDimAlpha(float sheetTranslation) {
   if (viewTransformer != null) {
     return viewTransformer.getDimAlpha(
         sheetTranslation,
         getMaxSheetTranslation(),
         getPeekSheetTranslation(),
         this,
         getContentView());
   } else if (defaultViewTransformer != null) {
     return defaultViewTransformer.getDimAlpha(
         sheetTranslation,
         getMaxSheetTranslation(),
         getPeekSheetTranslation(),
         this,
         getContentView());
   }
   return 0;
 }