I'm trying to copy the value of a date field in a custom module (Finanzierungen) to a related records in another module using functions 

and this is the function I used:

rec = zoho.crm.getRecordById("Finanzierungen",ID);

resp = zoho.crm.getRelatedRecords("Immobilien Abwicklung","Finanzierungen",ID,1);

mp = Map();

mp.put("Ankauf - Geld bezahlt",ifnull(rec.get("Ankauf - Geld bezahlt am"),''));

updateResp = zoho.crm.updateRecord("Immobilien Abwicklung",ele.get("id"),mp);

info updateResp;

but it does not work

can any one point out what's wrong with this function