code: public Transactions getInvoiceTransactions(final String invoiceId) {
          return doGET(Invoices.INVOICES_RESOURCE + "/" + invoiceId + Transactions.TRANSACTIONS_RESOURCE,
                       Transactions.class, new QueryParams());
      }
docs: Return all the transactions on an invoice. Only use this endpoint
  if you have more than 500 transactions on an invoice.
  <p>
  
  @param invoiceId String Recurly Invoice ID
  @return all the transactions on the invoice