sAction</a> will be called with <code>id</code> and one of
the possible <a href="dart-ui/SemanticsAction-class.html">SemanticsAction</a>s. Because the semantics tree is maintained
asynchronously, the <a href="dart-ui/Window/onSemanticsAction.html">Window.onSemanticsAction</a> callback might be called
with an action that is no longer possible.</p>
<p>The <code>label</code> is a string that describes this node. The <code>value</code> property
describes the current value of the node as a string. The <code>incr