code: func (a *alphabet) Index(t string) (int64, error) {
  	for i, char := range a.chars {
  		if char == t {
  			return int64(i), nil
  		}
  	}
  	return 0, fmt.Errorf("Element '%v' is not part of the alphabet", t)
  }
docs: // Index returns the index of the first instance of t in the alphabet, or an error if t is not present.