我试图以将零值和负值包含在结果计数器中的方式减去两个计数器对象，但没有得到所需的输出。示例代码块'`
1- dic = {'1':6 , '2':4 , '3':2}
2- dic2 = {'1':3 , '2':1 , '3':5}
3- obj1 = Counter(dic)
4- obj2 = Counter(dic2)
5- obj = obj1-obj2
6- print(obj)
#Output
Counter({'1':3 , '2':3}) #it omits the '3':-3 part
#In line 5 I also used subtract() but it is returning none
5 - obj = obj1.subtract(obj2)
#output
None