files</span><span class="op">)</span></span></span>
<span class="r-in"><span> <span class="fu"><a href="https://rdrr.io/r/utils/str.html" class="external-link">str</a></span><span class="op">(</span><span class="va">bt</span>, <span class="fl">1</span><span class="op">)</span></span></span>
<span class="r-out co"><span class="r-pr">#&gt;</span> List of 4</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  $ group_a:List of 23</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>   ..- att