meant
    one of the option returned by calling <code class="code">get_choices</code>. It does nothing
    if the returned list is empty.</p>

<p>The <code class="code">unit&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;...</code> thunking is meant to delay any potentially-slow
    computation (typically computing edit-distance with many things
    from the current environment) to when the hint message is to be
    printed. You should print an understandable error message before
    calling <code class="