code: public String getUnicodeLocaleType(String key) {
          if (!LocaleExtensions.isValidUnicodeLocaleKey(key)) {
              throw new IllegalArgumentException("Invalid Unicode locale key: " + key);
          }
          return extensions().getUnicodeLocaleType(key);
      }
docs: Returns the Unicode locale type associated with the specified Unicode locale key
  for this locale. Returns the empty string for keys that are defined with no type.
  Returns null if the key is not defined. Keys are case-insensitive. The key must
  be two alphanumeric characters ([0-9a-zA-Z]), or an IllegalArgumentException is
  thrown.
  
  @param key the Unicode locale key
  @return The Unicode locale type associated with the key, or null if the
  locale does not define the key.
  @throws IllegalArgumentException if the key is not well-formed
  @throws NullPointerException if <code>key</code> is null