for (int i = 0; i < id.length(); i++) {
            char c = id.charAt(i);
            if (!isValidCoordinateIdCharacter(c)) {
                return false;
            }
        }
        return true;
    }

    private boolean isValidCoordinateIdCharacter(char c) {

   *         .collect(
   *             flatteningToMultimap(
   *                  str -> str.charAt(0),
   *                  str -> str.substring(1).chars().mapToObj(c -> (char) c),
   *                  MultimapBuilder.linkedHashKeys().arrayListValues()::build));
   *
   * // is equivalent to
   *
   * static final ListMultimap<Character, Character> FIRST_LETTER_MULTIMAP;
   *