Problem with a custom function

I have tried to get this custom function working, but to no avail:
https://pitstop.manageengine.com/portal/en/kb/articles/if-technician-replies-to-the-unassigned-request-the-ticket-should-be-assigned-to-him

The custom function that I copied from the file wouldn't run, because at line 4 the context variable wasn't defined.

I have gotten past that. Now when I click Save and Test, I get this error in the output window:
"Error at line : 5, Argument type mismatch - Found 'TEXT' but Expected '[BIGINT]' for the function 'get'"

I get this error on line 5 even if I move the lines of code around.

I don't know why.

This is the first custom function i've tried to get working.

The code:

configuration = GlobalConfig1();

returnObj = Collection();
helpdeskID = returnObj.get("instance").get("id");
requestID = returnObj.get("id");
headers = {"authtoken":configuration.get("technicianKey"),"PORTALID":helpdeskID};