"n">i</span><span class="p">]</span> <span class="o">=</span> <span class="n">ajoin</span><span class="p">((</span><span class="n">Q</span><span class="p">,</span><span class="n">aS</span><span class="p">,</span><span class="n">bS</span><span class="p">))</span>
    
        
        <span class="k">elif</span> <span class="n">direction</span> <span class="o">==</span> <span class="s1">&#39;inverse&#39;</span><span class="p">:</span>

            <span class="c1"># get Q, M and a, b depending on input type: