Close the event store.

        Important to close to not have any file descriptor leakages.

def close(self):
        """Close the event store.

        Important to close to not have any file descriptor leakages.

        """
        if self.conn:
            self.conn.close()
            self.conn = None

        fname = os.path.basename(self._path)
        checksum_persister = _get_checksum_persister(self._path)
        hasher = _initialize_hasher(self._path)
        with contextlib.closing(checksum_persister):
            checksum_persister[fname] = hasher.hexdigest()