code: public GrpcServerBuilder keepAliveTime(long keepAliveTime, TimeUnit timeUnit) {
      mNettyServerBuilder = mNettyServerBuilder.keepAliveTime(keepAliveTime, timeUnit);
      return this;
    }
docs: Sets the keep alive time.
  
  @param keepAliveTime the time to wait after idle before pinging client
  @param timeUnit unit of the time
  @return an updated instance of this {@link GrpcServerBuilder}