Returns union of sets as a new set. basically it's
        Items are ordered by set1, set2, ...
        
        **中文文档**
        
        求多个有序集合的并集, 按照第一个集合, 第二个, ..., 这样的顺序。

def union(*argv):
        """Returns union of sets as a new set. basically it's
        Items are ordered by set1, set2, ...
        
        **中文文档**
        
        求多个有序集合的并集, 按照第一个集合, 第二个, ..., 这样的顺序。
        """
        res = OrderedSet()
        for ods in argv:
            res = res | ods
        return res