code: private function validateProperties(): void
      {
          if (!isset(self::$validMethods[$this->method])) {
              throw new InvalidArgumentException("Invalid HTTP method {$this->method}");
          }
  
          if (!isset(self::$validRequestTargetTypes[$this->requestTargetType])) {
              throw new InvalidArgumentException("Request target type {$this->requestTargetType} is invalid");
          }
      }
docs: Validates all the properties
  
  @throws InvalidArgumentException Thrown if any of the properties are invalid