xternal-link">print</a></span><span class="op">(</span><span class="fu"><a href="column_names.html">column_names</a></span><span class="op">(</span><span class="va">op_tree</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span>  <span class="fu"><a href="https://rdrr.io/r/base/print.html" class="external-link">print</a></span><span class="op">(</span><span class="fu"><a href="columns_used.html">columns_used</a></span><span class="op">(</span><span class="va">op_tree