Email_template.message

Hello guys i am trying to implement a function which sends multiple emails at once with the help of a template.
But my code doesn’t seem to be able to compile this line of code :

email_content = frappe.render_template(f"{email_template.message}", {“doc”: lead})

There must me a problem with email_template.message because i added print lines and it always stops at that point.

I hope someone can help me.
If you have any questions ask it.