vider-specific API. If the provider's EntityManagerFactory
 implementation does not support the specified class, the
 PersistenceException is thrown.</div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>cls</code> - the class of the object to be returned. This is
 normally either the underlying EntityManagerFactory
 implementation class or an interface that it implements.</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>an instance of the specified class</dd>
<dt><span class=