code: public function reverseTransform($address)
      {
          if (null === $address) {
              return null;
          }
  
          if (!$address instanceof ShipmentAddress) {
              throw new InvalidArgumentException("Expected instance of " . ShipmentAddress::class);
          }
  
          $data = [];
  
          foreach ($this->fields as $field) {
              $value = $this->accessor->getValue($address, $field);
              if (empty($value)) {
                  continue;
              }
  
              if ($value instanceof CountryInterface) {
                  $value = $value->getId();
              } elseif ($value instanceof StateInterface) {
                  $value = $value->getId();
              } elseif ($value instanceof PhoneNumber) {
                  $value = serialize($value);
              }
  
              $data[$field] = $value;
          }
  
          if (empty($data)) {
              return null;
          }
  
          return $data;
      }
docs: Transforms a shipment address in to an array.
  
  @param ShipmentAddress $address
  
  @return array|null