<h2>FlatMap</h2>
<p>Implement <code>Customer.getOrderedProducts()</code> and <code>Shop.getAllOrderedProducts()</code> using <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/kotlin.-iterable/flat-map.html"><code>flatMap</code></a>.</p><pre><code data-lang="text/x-kotlin">val result = listOf(&quot;abc&quot;, &quot;12&quot;).flatMap { it.toCharList() }
result == listOf(&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;1&#39;, &#39;2&#39;)
</code></pre>