如何通过函数修改标记为leaf的树中的每个叶值

class TreeNode:
    def __init__(self, value, left=None, right=None):
        self.value = value
        self.left = left
        self.right = right
        self.is_leaf = False

def modify_leaf_values(root):
    if root is None:
        return

    if root.left is None and root.right is None:
        root.value = modify_value(root.value)
        root.is_leaf = True
        return

    modify_leaf_values(root.left)
    modify_leaf_values(root.right)

def modify_value(value):
    # 在这里进行叶值的修改操作，可以根据具体需求进行实现
    # 这里只是一个示例，将叶值加上10
    return value + 10

# 构造一个示例树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)
root.right.left = TreeNode(6)
root.right.right = TreeNode(7)

# 修改叶值
modify_leaf_values(root)

# 打印修改后的树
def print_tree(root):
    if root is None:
        return

    print_tree(root.left)
    print(root.value)
    print_tree(root.right)

print_tree(root)

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17