Issue in bus141.py

Hi,
I am not clear when I see this line of code,would you help me to understand it?
https://github.com/xuwkk/gen_pandapower_pv/blob/8f90250d6453cee637c43bb0835326c24ef68f4e/bus141.py#LL69C2-L69C2

Thank you in advance.
Best Regards