Code example for adding attributes to items

Since mcreator does not yet support adding attributes to items, I am trying to figure out how to do it with code. If I could get an example, I could probably figure it out from there. To further clarify, I don't mean spawning an item in with a command. 

Also, I have tried using the attributes plugin (nerdy version) but could not get it to work with items. There is virtually no documentation for it and the plugin itself may be not working, hence why I am seeking help with code.