ArgumentException: An item with the same key has already been added when generating XML docs

[aelij]

Describe the issue or request
We encountered the following exception. Setting disable-xml-docs: true bypasses the problem. Note that the exception shows a test method name as the duplicate key, although we also set generate-test-project: false.

I can share the project internally.

System.ArgumentException: An item with the same key has already been added. Key: <test method name>
     at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
     at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
     at AutoRest.CSharp.AutoRest.Plugins.XmlFormatter.GetMethodsAsync(SyntaxTree syntaxTree) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\AutoRest\Plugins 
  \XmlFormatter.cs:line 156
     at AutoRest.CSharp.AutoRest.Plugins.XmlFormatter.FormatAsync(XmlDocWriter writer, SyntaxTree syntaxTree) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common 
  \AutoRest\Plugins\XmlFormatter.cs:line 23
     at AutoRest.CSharp.AutoRest.Plugins.GeneratedCodeWorkspace.GetGeneratedFilesAsync()+MoveNext() in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\AutoRest\ 
  Plugins\GeneratedCodeWorkspace.cs:line 146
     at AutoRest.CSharp.AutoRest.Plugins.GeneratedCodeWorkspace.GetGeneratedFilesAsync()+System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult()       
     at AutoRest.CSharp.AutoRest.Communication.StandaloneGeneratorRunner.RunAsync(CommandLineOptions options) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common 
  \AutoRest\Communication\StandaloneGeneratorRunner.cs:line 93
     at AutoRest.CSharp.AutoRest.Communication.StandaloneGeneratorRunner.RunAsync(CommandLineOptions options) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common 
  \AutoRest\Communication\StandaloneGeneratorRunner.cs:line 93
     at AutoRest.CSharp.Program.Run(CommandLineOptions options) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Program.cs:line 47
     at AutoRest.CSharp.Program.<>c.<<Main>b__2_0>d.MoveNext() in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Program.cs:line 29
  --- End of stack trace from previous location ---
     at AutoRest.CSharp.Program.Main(String[] args) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Program.cs:line 26
     at AutoRest.CSharp.Program.<Main>(String[] args)