>associative</span><span class="o">.</span><span class="n">associative</span>
      <span class="k">else</span><span class="p">:</span>
        <span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><span class="s">&#39;provide object with associative attribute for associative.&#39;</span><span class="p">)</span>

  <span class="k">def</span> <span class="nf">__neg__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
    <span class="sd">&quot