还开着几个 issue

按 issue 模型，["open", "closed", "open"]，open_issues 交回几？

issue 模型：is_assigned=指派给人了没（assignee 非空）；open_issues=还开着（非 closed）几个；closeable=关联 PR 已合并且子任务全完才能关。

def is_assigned(issue):
    """这个 issue 有没有指派给人（assignee 非空）。"""
    return bool(issue.get("assignee"))


def open_issues(issues):
    """还开着（状态不是 closed）的 issue 有几个。"""
    return sum(1 for s in issues if s != "closed")


def closeable(issue):
    """关联的 PR 已合并、且子任务全完，才能关。"""
    return issue.get("pr_merged", False) and all(issue.get("subtasks", []))

print(open_issues(["open", "closed", "open"]))