y the <em>union</em> of all currently-enabled <code>Tracing</code> objects and any categories
enabled using the <code>--trace-event-categories</code> flag.</p>
<p>Given the file <code>test.js</code> below, the command
<code>node --trace-event-categories node.perf test.js</code> will print
<code>'node.async_hooks,node.perf'</code> to the console.</p>
<pre><code class="language-js">const trace_events = require('trace_events');
const t1 = trace_events.createTracing({ categories: ['node.async_hooks'] });
const 