how to interact with the fellowers of the post-owner from like_by_tags

i see a example code from the instapy-quickstart template

session.like_by_tags(amount=random.randint(1, 15), use_smart_hashtags=True)

session.set_user_interact(amount=5, randomize=True, percentage=50,media='Photo')
session.set_do_follow(enabled=True, percentage=70)
session.set_do_like(enabled=True, percentage=70)

session.interact_user_followers([''], amount=random.randint(1, 10),randomize=True)

in this template,it firstly use like_by_tags,
then use set_user_interact,set_do_follow,
at last it use interact_user_followers,and the usernames list is ['']

what do you saya about this?