 template can either be a literal or an
<a href=/v1.10/zh/docs/reference/config/policy-and-telemetry/expression-language/>expression</a>. Please
note that if the datatype of a field is not
istio.mixer.adapter.model.v1beta1.Value, then the expression&rsquo;s
<a href=/v1.10/zh/docs/reference/config/policy-and-telemetry/expression-language/#type-checking>inferred type</a>
must match the datatype of the field.</p><p>Example config:</p><pre><code class=language-yaml>apiVersion: &quot;config.istio.io/v1alpha2&quo