code: public Checksum createChecksumForPaypalWithFee(Integer amount, String currency, String returnUrl, String cancelUrl,
        Fee fee, String appId) {
      return this.createChecksumForPaypalWithFeeAndDescription(amount, currency, returnUrl, cancelUrl, fee, null, appId);
    }
docs: Created a {@link Checksum} of {@link 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.
  @param fee
  A {@link Fee}.
  @param appId
  App (ID) that created this refund or null if created by yourself.
  @return {@link Checksum} object.