code: func (h *Client) PromotionCreative(promotionCreative string) *Client {
  	h.promotionCreative = promotionCreative
  	h.promotionCreativeSet = true
  	return h
  }
docs: // The creative associated with the promotion. Promotion index
  // must be a positive integer between 1 and 200, inclusive.
  // For analytics.js the Enhanced Ecommerce plugin must be installed
  // before using this field.