e> is a module of functions, here it only includes <code class="code">hash</code>, <code class="code">eq</code>.
<p>

    Unlike normal functions, when created, it comes with a unique identity (guaranteed
    by the type system).
<p>

    It can be created using function <a href="Belt_Id.html#VALhashableU"><code class="code">Belt_Id.hashableU</code></a> or <a href="Belt_Id.html#VALhashable"><code class="code">Belt_Id.hashable</code></a>.
<p>

    The idea of a unique identity when created is that it makes s