bbp_get_forum_parent_id( int $forum_id )

	function bbp_get_forum_parent_id( $forum_id = 0 ) {
		$forum_id  = bbp_get_forum_id( $forum_id );
		$parent_id = get_post_field( 'post_parent', $forum_id );

		return (int) apply_filters( 'bbp_get_forum_parent_id', (int) $parent_id, $forum_id );
	}