code: public static Validator validTrustManagerFactory() {
      return (s, o) -> {
        if (!(o instanceof String)) {
          throw new ConfigException(s, o, "Must be a string.");
        }
  
        String keyStoreType = o.toString();
        try {
          TrustManagerFactory.getInstance(keyStoreType);
        } catch (NoSuchAlgorithmException e) {
          ConfigException exception = new ConfigException(s, o, "Invalid Algorithm");
          exception.initCause(e);
          throw exception;
        }
      };
    }
docs: Validator is used to ensure that the TrustManagerFactory Algorithm specified is valid.
  @return