如何打印树的高度？

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def get_tree_height(root):
    if root is None:
        return 0
    else:
        left_height = get_tree_height(root.left)
        right_height = get_tree_height(root.right)
        return max(left_height, right_height) + 1

# 创建一个示例树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)
root.left.right = TreeNode(5)

# 打印树的高度
print("树的高度为:", get_tree_height(root))