def calculate_etag(file_path):
        """
        Calculate an etag value

        Args:
            a_file (pathlib.Path): The filepath to the

        Returns:
            String of the etag value to be sent back in header
        """
        stat = file_path.stat()
        etag = "%x-%x" % (stat.st_mtime_ns, stat.st_size)
        return etag