@Contract(pure = true)
  public static @Nullable String unpluralize(@NotNull String word) {
    String singular = Pluralizer.PLURALIZER.singular(word);
    if (singular != null) return singular;
    if (word.endsWith("es")) return nullize(trimEnd(word, "es", true));
    if (word.endsWith("s")) return nullize(trimEnd(word, "s", true));
    return null;
  }
@Contract(pure = true)
  public static @Nullable String unpluralize(@NotNull String word)