How to represent sum/union types in in json schema
<p>I am trying to document an existing use of JSON using json-schema.  The system permits the following two possabilities for one of the object attributes.</p>

<p>Either</p>

<pre><code>{
    "tracking_number" : 123
}
</code></pre>

<p>Or</p>

<pre><code>{
    "tracking_number" : [ 123, 124, 125 ]
}
</code></pre>

<p>How can I express this using json schema?</p>