code: public void setStatus(String service, ServingStatus status) {
      checkNotNull(status, "status");
      healthService.setStatus(service, status);
    }
docs: Updates the status of the server.
  @param service the name of some aspect of the server that is associated with a health status.
  This name can have no relation with the gRPC services that the server is running with.
  It can also be an empty String {@code ""} per the gRPC specification.
  @param status is one of the values {@link ServingStatus#SERVING},
  {@link ServingStatus#NOT_SERVING} and {@link ServingStatus#UNKNOWN}.