What does Zoho CRM respond to zoho.crm.getRelatedRecords if files are not attached?

What does Zoho CRM respond to zoho.crm.getRelatedRecords if files are not attached?

I can get attachments info by 
respond = zoho.crm.getRelatedRecords("Attachments","Invoices",ivId); 

I just want to know if record is not attached any file, what does this function respond? I try to check this with 'return respond', but nothing displayed.

Thanks in advance,
Kunio