code: public static void processKeysAttribute(final LmlParser parser, final Actor actor, final String rawAttributeData,
              final IntSet keys) {
          final String[] keyNames = parser.parseArray(rawAttributeData, actor);
          for (final String keyName : keyNames) {
              final int key = Keys.valueOf(keyName);
              if (key <= Keys.UNKNOWN) {
                  if (Strings.isInt(keyName)) {
                      keys.add(Integer.parseInt(keyName));
                  } else {
                      parser.throwErrorIfStrict("Unable to determine key for name: " + keyName
                              + ". Note that key name should match the EXACT name from Keys class (see Keys#valueOf(String)) or be the desired int value of key code.");
                  }
              } else {
                  keys.add(key);
              }
          }
      }
docs: Utility.
  
  @param parser parses template.
  @param actor contains the listener.
  @param rawAttributeData unparsed attribute data.
  @param keys handled keys set.