code: public void addExtraModule(String moduleId) {
  		if (extraModules == null) {
  			extraModules = new LinkedList<String>();
  		}
  		extraModules.add(moduleId);
  	}
docs: Adds the specified module to the list of extra modules.
  <p>
  Extra modules are included in the layer build that contains this
  module build.
  
  @param moduleId The module id to add to the before list