bp_rest_sanitize_group_types( string $value )

function bp_rest_sanitize_group_types( $value ) {
	if ( empty( $value ) ) {
		return null;
	}

	$types       = explode( ',', $value );
	$valid_types = array_intersect( $types, bp_groups_get_group_types() );

	return empty( $valid_types ) ? null : $valid_types;
}