code: public void unregister(Client client) {
          if (this.closed.get()) {
              // We are done. Nothing to do here.
              return;
          }
  
          Preconditions.checkNotNull(client, "client");
          synchronized (this.clients) {
              this.clients.remove(client);
          }
  
          log.info("{} Unregistered {}.", TRACE_OBJECT_ID, client);
      }
docs: Unregisters the given client from this CacheManager.
  
  @param client The client to unregister.