Search in Zoho Desk contacts by Boolean custom field - using deluge

Search in Zoho Desk contacts by Boolean custom field - using deluge

Hello, 

I am trying to search for contacts that cf_sync is false here is the script:
  1. contacts = zoho.desk.searchRecords(orgid,"contacts",{"customField1":"cf_sync:false"},0,100);
  2. info contacts;
but the output is:
{"errorCode":"UNPROCESSABLE_ENTITY","message":"The value passed for the 'Custom Field param wrongly passed' parameter is invalid."}