docs: @Override
      public void registerCommandHandler(String key, CommandHandler handler)
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(tc, "registerCommandHandler",
                          new Object[] { key, handler });
  
          // Table of keys and non-tx handlers is managed at ME level
          _messageProcessor.registerCommandHandler(key, handler);
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(tc, "registerCommandHandler");
      }