code: func (b *Bitmap) Add(a ...uint64) (changed bool, err error) {
  	changed = false
  	for _, v := range a {
  		// Create an add operation.
  		op := &op{typ: opTypeAdd, value: v}
  
  		// Write operation to op log.
  		if err := b.writeOp(op); err != nil {
  			return false, err
  		}
  
  		// Apply to the in-memory bitmap.
  		if b.DirectAdd(v) {
  			changed = true
  		}
  	}
  
  	return changed, nil
  }
docs: // Add adds values to the bitmap. TODO(2.0) deprecate - use the more general
  // AddN (though be aware that it modifies 'a' in place).