TreeNode () { return node("Root", node("Color", node("Red"), node("Green"), node("Blue")), node("Digit", node("One"), node("Two"), node("Three"), node("Four"), node("Five"), node("Six"), node("Seven"), node("Eight"), node("Nine")), node("Letter", node("Greek", node("Alpha"), node("Beta"), node("Gamma"), node("Delta"), node("Epsilon")))); }