Complex protractor selector

I am developing an angular application and want to test it using protractor. I have a repeater inside a repeater.

I select the first repeater like so:

var firstRepeater = element.all(by.repeater('item in set'));

Now, I see that protractor does not support a syntax like:

var secondRepeater = firstRepeater.element.all(by.repeater('item in set2'))

This throws an exception telling me that all is not defined. So if I understand correctly, one can only use firstRepeater.element and not firstRepeater.element.all ?

Then how can I select an item in the second repeater?