get a reference to the default <a href="/api/checkpoints/interfaces/checkpoints/checkpoints/"><code>Checkpoints</code></a> object (when called without a parameter), or one of the <a href="/api/checkpoints/interfaces/checkpoints/checkpoints/"><code>Checkpoints</code></a> objects that are named by <a href="/api/common/type-aliases/identity/id/"><code>Id</code></a> (when called with an <a href="/api/common/type-aliases/identity/id/"><code>Id</code></a> parameter).</p><section class="s2"><h2>Examples</h2><p>Thi