code: public function chargesCancel($id, $idempotency_key = null)
      {
          list($response) = $this->chargesCancelWithHttpInfo($id, $idempotency_key);
          return $response;
      }
docs: Operation chargesCancel
  
  Cancel a charge
  
  @param string $id The id of the authorised charge (required)
  @param string $idempotency_key The unique idempotency key. (optional)
  @throws \zipMoney\ApiException on non-2xx response
  @return \zipMoney\Model\Charge