static function preExport() {
		/**
		 * Let other plugins tweak things before exporting
		 *
		 * @since 4.4.0
		 */
		do_action( 'pb_pre_export' );

		// --------------------------------------------------------------------------------------------------------
		// Clear cache? Range is 1 hour.

		$last_export = get_option( 'pressbooks_last_export' );
		$within_range = time() - $last_export;
		if ( $within_range > ( HOUR_IN_SECONDS ) ) {
			\Pressbooks\Book::deleteBookObjectCache();
			update_option( 'pressbooks_last_export', time() );
		}

		static::$switchedLocale = switch_to_locale( self::locale() );
	}