code: public Invoices getAccountInvoices(final String accountCode) {
          return doGET(Accounts.ACCOUNTS_RESOURCE + "/" + accountCode + Invoices.INVOICES_RESOURCE,
                       Invoices.class, new QueryParams());
      }
docs: Lookup an account's invoices
  <p>
  Returns the account's invoices
  
  @param accountCode recurly account id
  @return the invoices associated with this account on success, null otherwise