code: func NewHook(callerLevels []logrus.Level, stackLevels []logrus.Level) LogrusStackHook {
  	return LogrusStackHook{
  		CallerLevels: callerLevels,
  		StackLevels:  stackLevels,
  	}
  }
docs: // NewHook is the initializer for LogrusStackHook{} (implementing logrus.Hook).
  // Set levels to callerLevels for which "caller" value may be set, providing a
  // single frame of stack. Set levels to stackLevels for which "stack" value may
  // be set, providing the full stack (minus logrus).