code: func (c Cigar) Lengths() (ref, read int) {
  	var con Consume
  	for _, co := range c {
  		con = co.Type().Consumes()
  		if co.Type() != CigarBack {
  			ref += co.Len() * con.Reference
  		}
  		read += co.Len() * con.Query
  	}
  	return ref, read
  }
docs: // Lengths returns the number of reference and read bases described by the Cigar.