lue should have</p></dd>


<dt id="arg-expected-length">expected_length<a class="anchor" aria-label="anchor" href="#arg-expected-length"></a></dt>
<dd><p>The expected length of value (usually to check if its a single value); 0 (default) indicates that length can be ignored</p></dd>

</dl></div>

    <div class="section level2">
    <h2 id="ref-examples">Examples<a class="anchor" aria-label="anchor" href="#ref-examples"></a></h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span cla