code: private function completeLeafValue(LeafType $returnType, &$result)
      {
          try {
              return $returnType->serialize($result);
          } catch (Exception $error) {
              throw new InvariantViolation(
                  'Expected a value of type "' . Utils::printSafe($returnType) . '" but received: ' . Utils::printSafe($result),
                  0,
                  $error
              );
          } catch (Throwable $error) {
              throw new InvariantViolation(
                  'Expected a value of type "' . Utils::printSafe($returnType) . '" but received: ' . Utils::printSafe($result),
                  0,
                  $error
              );
          }
      }
docs: Complete a Scalar or Enum by serializing to a valid value, throwing if serialization is not possible.
  
  @param  mixed $result
  
  @return mixed
  
  @throws Exception