function tec_get_venue_ids( $event_id = null ) {
	$event_id = Tribe__Events__Main::postIdHelper( $event_id );

	$venue_ids = [];

	if ( Tribe__Events__Main::instance()->isEvent( $event_id ) ) {
		$venue_ids = tribe_get_event_meta( $event_id, '_EventVenueID', false );

		// Protect against storing array items that render false, such as `0`.
		$venue_ids = array_filter( (array) $venue_ids );
	}

	/**
	 * Allows customization of the venue IDs retrieved for a specified event.
	 *
	 * @since 6.2.0
	 *
	 * @param int[] $venue_ids The venue IDs for the specified event.
	 * @param int   $event_id  The ID of the event whose venues are being looked for.
	 */
	return (array) apply_filters( 'tec_get_venue_ids', $venue_ids, $event_id );
}