code: func (p Bits) RowIDs() []uint64 {
  	if p.HasRowKeys() {
  		return nil
  	}
  	other := make([]uint64, len(p))
  	for i := range p {
  		other[i] = p[i].RowID
  	}
  	return other
  }
docs: // RowIDs returns a slice of all the row IDs.