已知有向图 \(G=(V, E)\) ,其中 \(V = \{v_{1}, v_{2}, v_{3}, v_{4}\}\) , \(E = \{ < v_{1}, v_{2}>, < v_{1}, v_{3}>, < v_{2}, v_{3}>, < v_{2}, v_{4}>, < v_{3}, v_{4}>\}\) ,则图 \(G\) 的拓扑序列是