code: func (ei *escapeInterpreter) runes() []rune {
  	switch ei.state {
  	case stateNone:
  		return []rune{0x1b}
  	case stateEscape:
  		return []rune{0x1b, ei.curch}
  	case stateCSI:
  		return []rune{0x1b, '[', ei.curch}
  	case stateParams:
  		ret := []rune{0x1b, '['}
  		for _, s := range ei.csiParam {
  			ret = append(ret, []rune(s)...)
  			ret = append(ret, ';')
  		}
  		return append(ret, ei.curch)
  	}
  	return nil
  }
docs: // runes in case of error will output the non-parsed runes as a string.