def require_keys(obj, keys: list[str], context: str = ""):
    if obj is None or not isinstance(obj, dict):
        raise KeyError(f"{context}: invalid_object")
    for k in keys:
        if k not in obj:
            raise KeyError(f"{context}: missing_key={k}")


def get_dict(obj, key: str, context: str = "") -> dict:
    if obj is None or not isinstance(obj, dict):
        raise KeyError(f"{context}: invalid_object")
    if key not in obj or obj[key] is None:
        raise KeyError(f"{context}: missing_key={key}")
    val = obj[key]
    if not isinstance(val, dict):
        raise KeyError(f"{context}: invalid_dict_key={key}")
    return val


def get_list(obj, key: str, context: str = "") -> list:
    if obj is None or not isinstance(obj, dict):
        raise KeyError(f"{context}: invalid_object")
    if key not in obj or obj[key] is None:
        raise KeyError(f"{context}: missing_key={key}")
    val = obj[key]
    if not isinstance(val, list):
        raise KeyError(f"{context}: invalid_list_key={key}")
    return val