span> <span class="n">index</span>  <span class="c1"># =&gt; also works!</span>

<span class="nb">len</span><span class="p">(</span><span class="n">index</span><span class="o">.</span><span class="n">ids</span><span class="p">)</span> <span class="c1"># =&gt; returns the number of non-deleted vectors</span>
<span class="nb">len</span><span class="p">(</span><span class="n">index</span><span class="p">)</span> <span class="c1"># =&gt; also returns the number of valid labels</span>

<span class="k">for</span>