What is the purpose of a topic sentence, typically?

It was fifteen minutes before i could work myself up to go and humble myself to a ; but i done it, and i warn’t ever sorry for it afterwards, neither. i didn’t do him no more mean tricks, and i wouldn’t done that one if i’d a knowed it would make him feel that way. in at least one hundred words, describe what central theme in the adventures of huckleberry finn emerges in this excerpt, and how its emergence relates to the social norms of the time.