Unable to locate and click checkbox ::before using RSelenium

I'm using Rselenium to locate and select the 'All Sites' check box in a drp down box with multiple options. I was able to locate and open the list with all the options in the drop down box but I have not been able to find select the first option 'All Sites' (see below screenshot).

I inspected the the 'All Sites' check box but I can't find an id (see below screenshot),

I tried using name, class name and xpath unsuccessfully. I have also tried some different approaches suggested in this website with no luck.

Does anyone know how to check the 'All Sites' box?

Thanks!