code: public Map<String,Element> getElementsById() {
  		synchronized(lock) {
  			if(elementsById == null) return Collections.emptyMap();
  			if(frozen) return elementsById;
  			return AoCollections.unmodifiableCopyMap(elementsById);
  		}
  	}
docs: Gets the elements indexed by id, in no particular order.
  Note, while the page is being created, elements with automatic IDs will not be in
  this map.  However, once frozen, every element will have an ID.
  
  @see  #freeze()