helper_map.go
func (h *HelperMap) Add(key string, helper interface{}) error {
	h.moot.Lock()
	defer h.moot.Unlock()
	if h.helpers == nil {
		h.helpers = map[string]interface{}{}
	}
	h.helpers[key] = helper
	return nil
}
func (h *HelperMap) Add(key string, helper interface{}) error {
	h.moot.Lock()
	defer h.moot.Unlock()
	if h.helpers == nil {
		h.helpers = map[string]interface{}{}
	}
	h.helpers[key] = helper
	return nil
}
// Add a new helper to the map. New Helpers will be validated to ensure they
// meet the requirements for a helper: