code: public OptionData getOption(String key) {
      if (key == null) throw new IllegalArgumentException(CLASS + ": key may not be null");
      if (!keys.containsKey(key)) throw new IllegalArgumentException(CLASS + ": unknown key: " + key);
      return keys.get(key);
    }
docs: Get the data for a specific option, identified by its key name (which is unique)
  <p>
  @param key The key for the option
  <p>
  @return The {@link OptionData} instance
  <p>
  @throws IllegalArgumentException If the <code>key</code> is <code>null</code> or unknown in this set