Missing code samples and variable declarations

The page is missing code samples and variable declarations, for example the variable `progressHandler` in the [Run the experiment](https://docs.microsoft.com/en-us/dotnet/machine-learning/how-to-guides/how-to-use-the-automl-api#run-the-experiment) snippet is never declared and I don't know how and where I should declare it (I'm still new to the ML.NET framework but I believe that how-to guides should make anyone make their snippets work independently of their previous knowdoledge on the subject)

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#### Document Details

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* ID: c3bb37d9-1c4d-5d5f-2ed6-2ef77f2cd627
* Version Independent ID: 80ed0d4d-63d3-49f0-ae42-d1f132137352
* Content: [How to use the ML.NET automated ML API - ML.NET](https://docs.microsoft.com/en-us/dotnet/machine-learning/how-to-guides/how-to-use-the-automl-api)
* Content Source: [docs/machine-learning/how-to-guides/how-to-use-the-automl-api.md](https://github.com/dotnet/docs/blob/main/docs/machine-learning/how-to-guides/how-to-use-the-automl-api.md)
* Product: **dotnet-ml**
* GitHub Login: @luisquintanilla
* Microsoft Alias: **luquinta**

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[Associated WorkItem - 261096](https://dev.azure.com/msft-skilling/Content/_workitems/edit/261096)