第四章#4.41代码出现问题

#4.41
faction <- get.vertex.attribute(karate, "Faction")

反馈的结果
Error in get.vertex.attribute(karate) : 
  get.vertex.attribute requires an argument of class network.

#4.42
func.class <- get.vertex.attribute(yeast.gc, "Class")
出现同样问题
Error in set.vertex.attribute(karate, "Faction") : 
  set.vertex.attribute requires an argument of class network.