human
Solve the following python programming problem given the following code:
@ async_test 
def testMultiple(self) : 
    'Tests that multiple allocations from the same sequence do
    not overlap.
    ' 
    allocs = [IdAllocator ('type'), IdAllocator ('type')] 
    num_ids = 3000 
    def _OnAllocated(id_lists) : 
        assert (len (id_lists) == 2) 
        id_set1 = set (id_lists [0]) 
        id_set2 = set (id_lists [1]) 
        assert (len (id_set1) == 3000) 
        assert (len (id_set2) == 3000) 
        assert id_set1.isdisjoint (id_set2) 
        self.stop () 
with util.ArrayBarrier (_OnAllocated) as b : 
        with util.ArrayBarrier (b.Callback ()) as b1 : 
            [allocs [0].NextId (b._client, b1.Callback ()) for i in xrange (num_ids)] 
with util.ArrayBarrier (b.Callback ()) as b2 : 
            [allocs [1].NextId (self._client, b2.Callback ()) for i in xrange (num_ids)] 

    
    

    Fix the buggy line: [allocs [0].NextId (b._client, b1.Callback ()) for i in xrange (num_ids)]
assistant
#Here is Python program to fix the buggy line: [allocs [0].

[allocs [0].NextId (self._client, b1.Callback ()) for i in xrange (num_ids)]