helper_map.go
func (h *HelperMap) AddMany(helpers map[string]interface{}) error {
	for k, v := range helpers {
		err := h.Add(k, v)
		if err != nil {
			return err
		}
	}
	return nil
}
func (h *HelperMap) AddMany(helpers map[string]interface{}) error {
	for k, v := range helpers {
		err := h.Add(k, v)
		if err != nil {
			return err
		}
	}
	return nil
}
// AddMany helpers at the same time.