s="fu"><a href="https://rdrr.io/r/base/class.html" class="external-link">class</a></span><span class="op">(</span><span class="va">df</span><span class="op">)</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="st">"keyed_df"</span>, <span class="st">"data.frame"</span><span class="op">)</span></span>
<span class="r-in"><span class="fu">is_keyed_df</span><span class="op">(</span><span class="va"