有几条拦路意见

按评审模型，两条 block、一条 nit，blocking 交回几？

评审模型：is_constructive=有具体建议 + 讲了为什么；blocking=几条拦路(severity=block)；ready_to_merge(意见, 批准数)=有批准且无拦路才能合。

def is_constructive(comment):
    """建设性意见：既给了具体建议、又说了为什么。"""
    return comment.get("suggestion", False) and comment.get("reason", False)


def blocking(comments):
    """有几条拦路意见（severity == "block"）。"""
    return sum(1 for c in comments if c.get("severity") == "block")


def ready_to_merge(comments, approvals):
    """有人批准、且没有拦路意见，才能合。"""
    return approvals >= 1 and blocking(comments) == 0

print(blocking([{"severity": "block"}, {"severity": "nit"}, {"severity": "block"}]))