   <span class="k">else</span><span class="p">:</span>
            <span class="k">if</span> <span class="n">subkey</span> <span class="ow">not</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">matrix</span><span class="p">[</span><span class="n">key</span><span class="p">]:</span>
                <span class="bp">self</span><span class="o">.</span><span class="n">matrix</span><span class="p">[</span><span class="n">key</span><span class="p">][</span><span