def setUp(self):
        super(SimpleInstanceTest, self).setUp()
        db_info = DBInstance(
            InstanceTasks.BUILDING, name="TestInstance")
        self.instance = SimpleInstance(
            None, db_info, InstanceServiceStatus(
                ServiceStatuses.BUILDING), ds_version=Mock(), ds=Mock())
        db_info.addresses = {"private": [{"addr": "123.123.123.123"}],
                             "internal": [{"addr": "10.123.123.123"}],
                             "public": [{"addr": "15.123.123.123"}]}
        self.orig_conf = CONF.network_label_regex
        self.orig_ip_regex = CONF.ip_regex
        self.orig_black_list_regex = CONF.black_list_regex
def addOperators(self, num, target):
        """
        Adapted from https://leetcode.com/discuss/58614/java-standard-backtrace-ac-solutoin-short-and-clear

        Algorithm:
        1. DFS
        2. Special handling for multiplication
        3. Detect invalid number with leading 0's
        :type num: str
        :type target: int
        :rtype: List[str]
        """
        ret = []
        self.dfs(num, target, 0, "", 0, 0, ret)
        return ret