Good job! It's time to wrap things up. First, let's review our new skills. We've learned:

1. To create a set from a list:

   set(list_name)

2. To eliminate duplicates from a list:

   list(set(list_name))

3. To combine multiple set operators:

   set_1 & set_2 & set_3 & set_4
   (set_1 | set_2) - set_3 - set_4

4. To check if set_1 is a subset/superset of set_2 using an operator:

   set_1 <= set_2
   set_1 >= set_2

5. Sets can be used to store all previous states of a state machine. To check if a new state already exists in the set:

   if new_state in previous_states:
     ...

Okay, how about a short quiz?