Changing Labels in Easy Post

Hi I have a question I’m trying to change the labels display names in Easy Post but I’m not sure on how that works. I copied someone’s code from over 5 years and but I tried using it and it’s not working on my end can does someone know how to change the display name from Acumatica. 

Shipment shipment = new Shipment() {
    to_address = toAddress,
    from_address = fromAddress,
    parcel = parcel
};

//DO THIS BEFORE CREATING!
shipment.options = new Dictionary<string, object>();
shipment.options.Add("print_custom_1", "this is some sample text");
shipment.options.Add("print_custom_2", "abc");
shipment.options.Add("print_custom_3", "xyz");

shipment.Create();
var lowestRate = shipment.LowestRate(includeServices: new List<string>() { "First" }, includeCarriers: new List<string>() { "USPS" });

shipment.Buy(lowestRate);

shipment.GenerateLabel("pdf");