Retrieving the APM transaction properties and its types in DSL Query - Elasticsearch

I am attempting to create a model class in my asp.net core web app project that contains the list of properties of an APM transaction. Whenever I run the command:

GET apm-*-transaction/_search
{
  "query": {
    "match": {
      "_id": "CZuK0nkBiU3wk_hrsN-K"
    }
  }
}

it will return the contents of that transaction....

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this is a continuation of the transaction properties from the DSL query cmd:

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I was reading up on attribute mapping for elasticsearch because I wanted to map the attribute Sec-Ch-Ua to variable named SecChUa so I did the following:

[PropertyName("Sec-Ch-Ua")]
public List<String> SecChUa {get; set;} // going to change <String> once I know its type

but realized I was doing it incorrectly and PropertyName should not be there, but replace that with its type... I needed to figure out the property type of Sec-Ch-Ua so I then did the following cmd GET /apm-*-transaction* which returned the properties and its type. So I did a search for Sec-Ch-Ua but it returns nothing.

Is this not the correct cmd to retrieve the list of properties of the apm transactions and its type?