code: func (v *view) clearBit(rowID, columnID uint64) (changed bool, err error) {
  	shard := columnID / ShardWidth
  	frag := v.Fragment(shard)
  	if frag == nil {
  		return false, nil
  	}
  	return frag.clearBit(rowID, columnID)
  }
docs: // clearBit clears a bit within the view.