code: public void add(ConfigurationMetadataProperty property,
  			ConfigurationMetadataSource source) {
  		if (source != null) {
  			putIfAbsent(source.getProperties(), property.getId(), property);
  		}
  		putIfAbsent(getGroup(source).getProperties(), property.getId(), property);
  	}
docs: Add a {@link ConfigurationMetadataProperty} with the
  {@link ConfigurationMetadataSource source} that defines it, if any.
  @param property the property to add
  @param source the source