code: func iterBitmapsDistinct(skip *bitmap.Bitmap, bms ...bitmap.Bitmap) iter.Func {
  	return func(cb iter.Callback) {
  		for _, bm := range bms {
  			if !iter.All(func(i interface{}) bool {
  				skip.Add(i.(int))
  				return cb(i)
  			}, bitmap.Sub(bm, *skip).Iter) {
  				return
  			}
  		}
  	}
  }
docs: // Emits the indices in the Bitmaps bms in order, never repeating any index.
  // skip is mutated during execution, and its initial values will never be
  // emitted.