enerated id is not guaranteed to be available until after
  the database insert has occurred.
  Returns null if the entity does not yet have an id.</div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>entity</code> - entity instance</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>id of the entity</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/IllegalArgumentException.html?is-ext