code: func NewHookForLevels(token string, env string, levels []logrus.Level) *Hook {
  	return &Hook{
  		Client:          roll.New(token, env),
  		triggers:        levels,
  		ignoredErrors:   make([]error, 0),
  		ignoreErrorFunc: func(error) bool { return false },
  		ignoreFunc:      func(error, map[string]string) bool { return false },
  	}
  }
docs: // NewHookForLevels provided by the caller. Otherwise works like NewHook.