type set of <code>I</code>.
</li>
</ul>

<p>
A value of type <code>T</code> implements an interface if <code>T</code>
implements the interface.
</p>

<h3 id="Map_types">Map types</h3>

<p>
A map is an unordered group of elements of one type, called the
element type, indexed by a set of unique <i>keys</i> of another type,
called the key type.