code: public GenericTemplateElementBuilder addBuyButton(String payload,
  			PaymentSummary paymentSummary) {
  		Button button = ButtonFactory.createBuyButton(payload, paymentSummary);
  		this.element.addButton(button);
  		return this;
  	}
docs: Adds a buy button on a generic template.
  
  @param payload
  the payload
  @param paymentSummary
  the payment summary
  @return this builder.