ss="o">=</span> <span class="nb">len</span><span class="p">(</span><span class="n">system</span><span class="p">)</span>
        <span class="k">if</span> <span class="n">centers</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
            <span class="n">centers</span> <span class="o">=</span> <span class="p">[</span><span class="kc">None</span><span class="p">]</span> <span class="o">*</span> <span class="n">n_samples</span>
        <span class="k">if</span> <span cla