code: def get_blocked_usernames():
      
      if config.DISABLE_USERNAME_LOCKOUT:
          # There are no blocked usernames since we disabled them.
          return []
      key = get_username_blocked_cache_key("*")
      key_list = [redis_key.decode('utf-8')
                  for redis_key in REDIS_SERVER.keys(key)]
      return strip_keys(key_list)
docs: get a list of blocked usernames from redis