cp_recognized_relationship_objects()

function cp_recognized_relationship_objects() {

	// Names of post types (including custom post types).
	$post_types = get_post_types();

	// Names of taxonomies (including custom taxonomies).
	$taxonomies = get_taxonomies();

	// Merge arrays and add comments, users, and thumbnails.
	$objects = array_merge( $post_types, $taxonomies );
	$objects['comment']   = 'comment';
	$objects['user']      = 'user';
	$objects['thumbnail'] = 'thumbnail';
	/**
	 * Filter enabling modification of the list of recognized relationship objects.
	 *
	 * @since CP-2.2.0
	 *
	 * @param  array  $objects  Default array of recognized relationship objects.
	 *
	 * @return array  $objects  Filtered array of recognized relationship objects.
	 */
	return apply_filters( 'recognized_relationship_objects', $objects );
}