ss="docutils literal notranslate"><span class="pre">valid(Year,Month,Day)</span></code></div>
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<div class="line"><strong>Mode and number of proofs:</strong></div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">valid(&#64;integer,&#64;integer,&#64;integer)</span></code> - <code class="docutils literal notranslate"><span class="pre">zero_or_one</span></code></div>
</div>
</div>
</section>
</section>
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<section id="protected-p