def has_index_together_changed(old_model_sig, new_model_sig):
    """Returns whether index_together has changed between signatures."""
    old_meta = old_model_sig['meta']
    new_meta = new_model_sig['meta']
    old_index_together = old_meta.get('index_together', [])
    new_index_together = new_meta['index_together']

    return list(old_index_together) != list(new_index_together)