private static function _gatherChildren(PolicyNode ...$nodes): array
    {
        $children = array();
        foreach ($nodes as $node) {
            $children = array_merge($children, $node->children());
        }
        return $children;
    }
private static function _gatherChildren(PolicyNode ...$nodes): array
    {
        $children = array();
        foreach ($nodes as $node) {
            $children = array_merge($children, $node->children());
        }
        return $children;
    }
private static function _gatherChildren ( PolicyNode ... $ nodes ) : array { $ children = array ( ) ; foreach ( $ nodes as $ node ) { $ children = array_merge ( $ children , $ node -> children ( ) ) ; } return $ children ; }
Gather all children of given nodes to a flattened array.

@param PolicyNode ...$nodes
@return PolicyNode[]
Gather all children of given nodes to a flattened array .