code: @Override
      public Object getIdentifierValue(Identifier id,
                                       boolean ignoreType)
                      throws BadMessageFormatMatchingException {
          return getIdentifierValue(id, ignoreType, null, false);
      }
docs: /*
  Evaluate the message field determined by the given Identifier
  See the following method for more information.
  
  Javadoc description supplied by MatchSpaceKey interface.