The 3DEXPERIENCE mobile app needs to display its most active users first. Given a list of user records, return the records sorted by descending activity count. If two users have the same activity count, order them by ascending user_id for deterministic output.
Return a new list and do not modify the input list.
Implement sort_users(users), where users is a list of dictionaries. Each dictionary contains a string user_id and a non-negative integer activity_count. Return a list containing the same dictionaries in the required order.
def sort_users(users):