ot empty.</p><table class=message-fields><thead><tr><th>Field</th><th>Type</th><th>Description</th><th>Required</th></tr></thead><tbody><tr id=Rule-from><td><code>from</code></td><td><code><a href=#Rule-From>From[]</a></code></td><td><p>Optional. from specifies the source of a request.</p><p>If not set, any source is allowed.</p></td><td>No</td></tr><tr id=Rule-to><td><code>to</code></td><td><code><a href=#Rule-To>To[]</a></code></td><td><p>Optional. to specifies the operation of a request.</p><p>If not set