public function set_tax_class( $class ) {
		$class         = sanitize_title( $class );
		$class         = 'standard' === $class ? '' : $class;
		$valid_classes = $this->get_valid_tax_classes();

		if ( ! in_array( $class, $valid_classes, true ) ) {
			$class = '';
		}

		$this->set_prop( 'tax_class', $class );
	}