ID vs. Class in Accordeon API-Doc

[bbmxxc]

On http://api.jqueryui.com/accordion/
the Example states

<div id="accordion">
  <h3>First header</h3>
  <div>First content panel</div>
  <h3>Second header</h3>
  <div>Second content panel</div>
</div>

But the node #accordion is always referenced as ".accordion" in later steps.
For example:

$( ".selector" ).accordion({
  active: 2
});