an> <span class="nv">source</span><span class="p">:</span> <span class="p">[</span><span class="kt">ArraySection</span><span class="o">&lt;</span><span class="kt">Model</span><span class="p">,</span> <span class="kt">String</span><span class="o">&gt;</span><span class="p">]</span> <span class="o">=</span> <span class="p">[</span>
    <span class="kt">ArraySection</span><span class="p">(</span><span class="nv">model</span><span class="p">:</span> <span class="o">.</span><span class="n">a</span><span class="p