class="o">.</span><span class="n">permutation</span><span class="p">(</span><span class="n">len_</span><span class="p">)</span>
        <span class="n">t</span> <span class="o">=</span> <span class="n">t</span><span class="p">[</span><span class="n">idx_</span><span class="p">]</span>
        <span class="n">mu</span> <span class="o">=</span> <span class="n">mu</span><span class="p">[</span><span class="n">idx_</span><span class="p">]</span>
        
    <span class="c1"># Ensure enough unique pairs can be 