Cómo peinar la hoja de fondo
<style name="BottomSheet" parent="Widget.Design.BottomSheet.Modal">
<item name="android:background">@android:color/transparent</item>
</style>
<style name="BottomSheetMenu" parent="Theme.Design.BottomSheetDialog">
<item name="bottomSheetStyle">@style/BottomSheet</item>
</style>
</ProgAli>