code: func (le *LeaderElector) Check(maxTolerableExpiredLease time.Duration) error {
  	if !le.IsLeader() {
  		// Currently not concerned with the case that we are hot standby
  		return nil
  	}
  	// If we are more than timeout seconds after the lease duration that is past the timeout
  	// on the lease renew. Time to start reporting ourselves as unhealthy. We should have
  	// died but conditions like deadlock can prevent this. (See #70819)
  	if le.clock.Since(le.observedTime) > le.config.LeaseDuration+maxTolerableExpiredLease {
  		return fmt.Errorf("failed election to renew leadership on lease %s", le.config.Name)
  	}
  
  	return nil
  }
docs: // Check will determine if the current lease is expired by more than timeout.