an><span class="bp">self</span><span class="o">.</span><span class="n">len_variables</span><span class="p">)</span>
        <span class="bp">self</span><span class="o">.</span><span class="n">pm_cov</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">zeros</span><span class="p">((</span><span class="bp">self</span><span class="o">.</span><span class="n">len_variables</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n