Python itertools.combinations : Itertool.combination code gives me all combination for a target value 
I have an array 

    a=[1,1,2,-2,-4] target =0

output I get from:

    Itertools.combination is: [(2, -2), (1, 1, -2), (1, 1, 2, -4)].

But the concern is:- Once the number is used, it should not get repeated.
Required Output:- [(2,-2)] #As 2,-2 pair nets to 0. Code should not use 2 again to sum:1,1,2 and net that off with -4. [I dont want numbers to get repeated once it is used in one of the pair.]

    # Reference code:-
    
        import itertools
        import numpy as np
        
        def subset_sum(target, numbers):
        
            array_num=np.array(numbers)
            for size in xrange(1, len(array_num) + 1):
                 for c in itertools.combinations(array_num, size):
                     if sum(c) == target:
                       temp_var.append(c)
                       print "Length of array is ",len(array_num)
        
            return temp_var
        
        numbers=[1,1,2,-2,-4]
        target=0
        output=subset_sum(numbers)
        print output

