def _load_raw_data(self, resource_name):
        """Extract raw data from resource

        :param resource_name:
        """
        # Instantiating the resource again as a simple `Resource` ensures that
        # ``data`` will be returned as bytes.
        upcast_resource = datapackage.Resource(
            self.__resources[resource_name].descriptor,
            default_base_path=self.__base_path)
        return upcast_resource.data