code: @Nullable
    public static String quote(@Nullable final String str) {
      return str != null ? "'" + str + "'" : null;
    }
docs: Quote the given {@code String} with single quotes.
  
  @param str the input {@code String} (e.g. "myString")
  @return the quoted {@code String} (e.g. "'myString'"), or {@code null} if the input was
  {@code null}