能部署吗、推进到哪

（env_of(分支)：main 上 prod、其它上 staging；can_deploy(全绿, 已审批) 两者都真才 True；stage_flow(各环境结果) 按顺序逐级推进、遇失败停，交回推进到的最后一个环境。）

问「全绿但没审批能不能部署」，以及一次 staging 过、prod 挂的推进到哪：

def env_of(branch):
    """按分支决定部署到哪个环境：main 上 prod，其它分支上 staging。"""
    return "prod" if branch == "main" else "staging"


def can_deploy(green, approved):
    """流水线全绿、且审批通过，才允许部署。"""
    return green and approved


def stage_flow(steps):
    """steps: [(环境, 通过?)]，按顺序逐级推进（如 staging→prod），遇失败就停。交回推进到的最后一个环境；一个都没过交回空串。"""
    reached = ""
    for env, ok in steps:
        if not ok:
            return reached
        reached = env
    return reached

a = can_deploy(True, False)
b = stage_flow([("staging", True), ("prod", False)])
print(str(a) + "/" + b)