def METHOD_NAME(self):
    hmap = self.fill_hashmap()
    # preparing keys and new values arrays
    keys = (hmap.Key * self.MAPSIZE)()
    new_values = (hmap.Leaf * self.MAPSIZE)()
    for i in range(self.MAPSIZE):
        keys[i] = ct.c_int(i)
        new_values[i] = ct.c_int(-1)
    hmap.items_update_batch(keys, new_values)
    # check the update has worked, i.e sum of values is -NUM_KEYS
    count = sum(v.value for v in hmap.values())
    self.assertEqual(count, -1*self.MAPSIZE)