code: function extractPlaceholderToIds(messageBundle) {
  	      var messageMap = messageBundle.getMessageMap();
  	      var placeholderToIds = {};
  	      Object.keys(messageMap).forEach(function (msgId) {
  	          placeholderToIds[msgId] = messageMap[msgId].placeholderToMsgIds;
  	      });
  	      return placeholderToIds;
  	  }
docs: Generate a map of placeholder to message ids indexed by message ids