Missing potentially required value [energy efficiency class]

Hi!

In my Google Merchant account i’m getting the following issue displayed: Missing potentially required value [energy efficiency class]

There is any way to add a field in my product pages with the energy efficiency class label and then add a field into the feed that your module creates?

How can I do this? Which plugin do you recommend for adding the energy efficiency class to the product pages or it can be added with a custom field without a pluging?

Once added this energy efficiency class label into my product pages how can I add this field to the product feed in a way that Google Merchant reads the data and publish it correctly to avoid the issue meant before?

I wait for your answer

Kind regards

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