def save_signature(filename, selected, threshold=0.75):
    """Save signature summary."""
    with open(filename, 'w') as f:
        line_drawn = False
        for k in reversed(sorted(selected, key=selected.__getitem__)):
            if not line_drawn and float(selected[k]) < threshold:
                line_drawn = True
                f.write('=' * 40)
                f.write('\n')
            f.write('{} : {}\n'.format(k, selected[k] * 100.0))
