def translation_for(key, lang)
      self.translations.find_or_initialize_by(translation_key_id: key.id, lang: lang.to_s, translator_type: self.class.name)
    end
def translation_for(key, lang)
      self.translations.find_or_initialize_by(translation_key_id: key.id, lang: lang.to_s, translator_type: self.class.name)
    end
returns the translation a user has made for a certain key in a certain language