code: private static <T> EventInterfaceDescriptor<T> getDescriptor(Class<T> t) {
          EventInterfaceDescriptor<T> r = descriptors.get(t);
          if(r==null) {
              r = new EventInterfaceDescriptor<T>(t);
              descriptors.put(t,r);
          }
          return r;
      }
docs: Gets the descriptor for the given type.