title: Autorest code customization does not work
body: <p>What i am doing wrong, when code customization does not work?</p>
  <p>readme.md</p>
  <pre class="lang-yaml prettyprint-override"><code>require: $(this-folder)/../readme.md
  input-file: $(this-folder)/../../swagger/TaxManagementAPI/swagger.yaml
  output-folder: ./Generated
  csharp: true
  namespace: TaxManagement.RestClient
  </code></pre>
  <p>MessageBaseTest.cs</p>
  <pre><code>using Azure.Core;
  namespace TaxManagement.RestClient.Models
  {
      [CodeGenModel(&quot;MessageBase&quot;)]
      public partial class MessageBaseTest { }
  }
  </code></pre>
  <p>Then i run</p>
  <p><code>autorest --use:@autorest/csharp@3.0.0-beta.20210210.4  .\readme.md </code></p>
  <p>and nothing has changed in Generated/MessageBase.cs.
  I also tried it in sample repo. However, the result was the same.
  <a href="https://github.com/Azure/autorest.csharp/tree/feature/v3/samples/Azure.Storage.Tables" rel="nofollow noreferrer">https://github.com/Azure/autorest.csharp/tree/feature/v3/samples/Azure.Storage.Tables</a></p>