code: public Checksum createChecksumForPaypal(Integer amount, String currency, String returnUrl, String cancelUrl) {
      return this.createChecksumForPaypalWithDescription(amount, currency, returnUrl, cancelUrl, null);
    }
docs: Created a {@link Checksum} of {@link Checksum#type Checksum.type} with amount in the given currency.
  
  @param amount
  Amount (in cents) which will be charged.
  @param currency
  ISO 4217 formatted currency code.
  @param returnUrl
  URL to redirect customers to after checkout has completed.
  @param cancelUrl
  URL to redirect customers to after they have canceled the checkout. As a result, there will be no transaction.
  @return {@link Checksum} object.