Create Issue with proforma form

I am trying initially to use Scriptrunner hapi to create an issue with a proforma form attached, I am happy to not use HAPI if theres no option but i want to create a JSM ticket with a pre-created Proforma form attached but i cannot seem to get it to work. Proforma forms are listed in the Entity property of an issue so I am trying to add the form using setProperty Method but anything i attempt does not work (creates issue but not attach the form)

Please help

Issues.create(“TEST”,“TASK”) {

setSummary(“IM HAPI”)

setRequestType(“Test Request”)

setReporter(“Test User”)

//Try to set property not sure how to get this line to work

setProperty(proformaKey, proformaValue)