ode></td><td><p>Operation specifies the operation of a request.</p></td><td>No</td></tr></tbody></table></section><h2 id=Source>Source</h2><section><p>Source specifies the source identities of a request.</p><table class=message-fields><thead><tr><th>Field</th><th>Type</th><th>Description</th><th>Required</th></tr></thead><tbody><tr id=Source-principals><td><code>principals</code></td><td><code>string[]</code></td><td><p>Optional. A list of source peer identities (i.e. service account), which
matches to the 