vue-wp/plugins/posts-to-posts/vendor/scribu/lib-posts-to-posts/url-query.php

<?php

class P2P_URL_Query {

	static function get_custom_qv() {
		return array( 'connected_type', 'connected_items', 'connected_direction' );
	}

	static function init() {
		add_filter( 'query_vars', array( __CLASS__, 'query_vars' ) );
	}

	// Make the query vars public
	static function query_vars( $public_qv ) {
		return array_merge( $public_qv, self::get_custom_qv() );
	}
}