[Question] Is there a way to see all defined variables in a template?

[Zalimben]

For example, I am adding userName to the model and I know I can access the value by {{ userName }} in my template.
But I want to list all defined variables (keys) in a template like {{ _context.key }} {{ _context.value }} and see in my template something like userName: Jhon Doe.

Is that possible? Or is there a way to see all defined variables in a template?