code: public Boolean hasOriginalInvoices() {
          return originalInvoices != null && originalInvoices.getHref() != null && !originalInvoices.getHref().isEmpty();
      }
docs: For use with RecurlyClient.getOriginalInvoices(). Check if an invoice had an <original_invoices> link
  in the XML from the API.
  
  @return true if there are original invoices associated with this invoice