code: public Set<GwtModule> getInherits()
  		throws GwtModuleReaderException
      {
          if ( inherits != null )
          {
              return inherits;
          }
  
          inherits = new HashSet<GwtModule>();
          addInheritedModules( inherits, getLocalInherits() );
  
          return inherits;
      }
docs: Build the set of inhertied modules. Due to xml inheritence mecanism, there may be cicles in the inheritence
  graph, so we build a set of inherited modules