<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_id_from_user(user):
 """Get an ID from a user, creates if necessary"""

    id = r_client.hget('user-id-map', user)
    if id is None:
        id = str(uuid4())
        r_client.hset('user-id-map', user, id)
        r_client.hset('user-id-map', id, user)
    return id