def temporary(cls):
        """
        Returns a temporary hdf5 file, open for writing.
        The temporary name is stored in the .path attribute.
        It is the user responsability to remove the file when closed.
        """
        fh, path = tempfile.mkstemp(suffix='.hdf5')
        os.close(fh)
        self = cls(path, 'w')
        self.path = path
        return self