Issue with RAG|ChatWithRetrieval sample

[davefloodnz]

Hi Willem. Very useful book, thankyou.

I'm having an issue with the RAG|ChatWithRetrieval sample, maybe you could suggest a fix?

It's failing on line 28 in the QuestionAnsweringBot() class ... kernel.Plugins.AddFromObject(textSearch.CreateWithSearch("SearchPlugin"));

With System.ArgumentException: 'The Microsoft.SemanticKernel.DefaultKernelPlugin instance doesn't implement any [KernelFunction]-attributed methods.'

CoPilot says: You are getting this error because either:
• The class returned by CreateWithSearch does not have any [KernelFunction]-decorated methods.
• Or, CreateWithSearch is returning a default plugin (like DefaultKernelPlugin) that is not properly implemented.
To fix this, ensure that the class returned by CreateWithSearch has at least one public method decorated with [KernelFunction]. If you need more information, please provide the code for VectorStoreTextSearch and its CreateWithSearch method.

As this code is part of Semantic Kernel, I'm not sure how to proceed. Any ideas?