code: public final <T> void registerType(Class<T> runtimeClass, TypeHandler<T> handler) {
          if (started) {
              // Can't add any more metrics anyway; harmless
              return;
          }
          typeHandlers.put(runtimeClass, handler);
      }
docs: /*
  (non-Javadoc)
  @see io.pcp.parfait.pcp.PcpWriter#registerType(java.lang.Class,
  io.pcp.parfait.pcp.types.TypeHandler)