从最后一个往回走一步是谁

运行下面这段程序：

class DNode:
    def __init__(self, name):
        self.name = name
        self.next = None
        self.prev = None

def dbuild(names):
    head = None
    tail = None
    for x in names:
        nd = DNode(x)
        if head is None:
            head = nd
        else:
            tail.next = nd
            nd.prev = tail
        tail = nd
    return head, tail

head, tail = dbuild(["阿岚", "小满", "阿泰", "南风"])
print(tail.prev.name)