Array Set doesn't have rowKey specified when passing an arrayset attribute in config json

Summary:

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I have a library function that parses an inputted catalog string and builds the config data json string to be used in the _configure Rest API.

This works fine with other attributes but I have now been tasked with adding array set attibute values.

I searched the community and thanks to Burkhard, I beleive I have the format correct but I recieve the following error.
{"title":"Array Set gasType_ati doesn't have rowKey specified for its array items."}]

The atribute name is gasType_ati. It is a string value of 2 charactors. The set type is "None".