class TreeNode:
    def __init__(self, value):
        self.value = value
        self.children = []


def print_tree(node, indent=0):
    print(" " * indent + str(node.value))
    for child in node.children:
        print_tree(child, indent + 1)


def ceate_tree():
    A, B, C, D, E, F = [TreeNode(x) for x in 'ABCDEF']
    A.children = [B, D]
    B.children = [C]
    D.children = [E, F]
    return A


if __name__ == '__main__':
    root = ceate_tree()
    print_tree(root)

输出

A
 B
  C
 D
  E
  F