I have created an email template for custom record. I want to send email by SuiteScript with that template. I used

email.mergeEmail()

but I'm not sure how to add data sources to email. in pdf template, we add data source by

renderer.addRecord()

and

renderer.addCustomDataSource()

And we can use that in PDF template by record.fieldid, Could someone help me how to do those same things in email renderer please?