pan class="normal">43</span>
<span class="normal">44</span>
<span class="normal">45</span>
<span class="normal">46</span></pre></div></td><td class="code"><div><pre><span></span><code><span class="k">def</span> <span class="fm">__len__</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">int</span><span class="p">:</span>
    <span class="sd">&quot;&quot;&quot;Returns the number of molecules in the dataset.</span>

<span class="sd">