public function get($id)
    {
        foreach ($this->instructions as $instruction) {
            if (!$instruction instanceof Node && !$instruction instanceof Subgraph) {
                continue;
            }

            if ($instruction->getId() == $id) {
                return $instruction;
            }
        }

        throw new \InvalidArgumentException(sprintf('Found no node or graph with id "%s" in "%s".', $id, $this->id));
    }