def save(self, data, fname, header=None):
        """
        Save data on fname.

        :param data: numpy array or list of lists
        :param fname: path name
        :param header: header to use
        """
        write_csv(fname, data, self.sep, self.fmt, header)
        self.fnames.add(getattr(fname, 'name', fname))
Save data on fname.

        :param data: numpy array or list of lists
        :param fname: path name
        :param header: header to use