'user_id starts following target_user_id
:param user_id: the user which is doing the following
:param target_user_id: the user which is being followed
:param async: controls if the operation should be done via celery'

def follow_user(self, user_id, target_user_id, async=True):

    self.follow_many_users(user_id, [target_user_id], async)
