I have a dataframe df
ID active_seconds domain subdomain search_engine search_term
0120bc30e78ba5582617a9f3d6dfd8ca 35 vk.com vk.com None None
0120bc30e78ba5582617a9f3d6dfd8ca 54 vk.com vk.com None None
0120bc30e78ba5582617a9f3d6dfd8ca 34 vk.com vk.com None None
16c28c057720ab9fbbb5ee53357eadb7 4 facebook.com facebook.com None None
16c28c057720ab9fbbb5ee53357eadb7 4 facebook.com facebook.com None None
16c28c057720ab9fbbb5ee53357eadb7 8 facebook.com facebook.com None None
0120bc30e78ba5582617a9f3d6dfd8ca 16 megarand.ru megarand.ru None None
0120bc30e78ba5582617a9f3d6dfd8ca 6 vk.com vk.com None None
I need to change df. If to ID subdomain[i] == subdomain[i-1] I should union this string and active_seconds[i-1] + active_seconds[i].
From this df I want to get
ID active_seconds domain subdomain search_engine search_term
0120bc30e78ba5582617a9f3d6dfd8ca 123 vk.com vk.com None None
16c28c057720ab9fbbb5ee53357eadb7 16 facebook.com facebook.com None None
0120bc30e78ba5582617a9f3d6dfd8ca 16 megarand.ru megarand.ru None None
0120bc30e78ba5582617a9f3d6dfd8ca 6 vk.com vk.com None None
What sould I use to do it?

domain[i] != domain[i-1]