层序走到第四个是谁

运行下面这段程序：

class TNode:
    def __init__(self, name):
        self.name = name
        self.left = None
        self.right = None

def build():
    root = TNode("总部")
    root.left = TNode("华北")
    root.right = TNode("华南")
    root.left.left = TNode("北京")
    root.left.right = TNode("天津")
    root.right.right = TNode("广州")
    return root

q = [build()]
order = []
while len(q) > 0:
    node = q.pop(0)
    order.append(node.name)
    if node.left is not None:
        q.append(node.left)
    if node.right is not None:
        q.append(node.right)
print(order[3])