public function get_engines_map() {
		$map = array(
			self::NONE      => 'Tribe__Events__Pro__Recurrence__Engines__Null',
			self::VERSION_1 => 'Tribe__Events__Pro__Recurrence__Engines__Version_1',
		);

		/**
		 * Filters the slugs and classes of the recurrence backend engines available.
		 *
		 * @since 4.7
		 *
		 * @param array $map A map in the shape [ <slug> => <class> ].
		 */
		return apply_filters( 'tribe_events_pro_recurrence_backend_engines', $map );
	}