Howto add a counter to each row in MultiModelForm

I am using the extension MultiModelForm.

Is there a way to add a counter at the beginning of each row?

I looked into the code of the class MultiModelForm. I see that there exists a counter-variable $idx inside the function "run ()". But I cannot find a way to display this counter inside the form. If I echo it, then the counter appears of course outside the form.