Exercise 1: Adding get_item_count() to the Stateless Service — Possible Solution
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THE NEW METHOD
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    class StatelessCartService:
        # ...existing add_item()/get_cart() unchanged...
        def get_item_count(self, current_cart):
            return len(current_cart)

Follows this chapter's own StatelessCartService shape exactly - it
takes current_cart as an argument, just like get_cart() and
add_item(), and holds no state of its own between calls.

VERIFYING IT WORKS AFTER A SIMULATED RESTART
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    cart after two adds: ['Widget', 'Gadget']
    item count from a fresh service instance, given only client-supplied cart data: 2

Two items were added via the existing add_item() method, producing a
cart the CLIENT holds onto. A brand-new StatelessCartService instance
- simulating this chapter's own server-restart scenario - correctly
reports a count of 2, using only the cart data supplied by the client
in the call itself.

WHY THIS CONFIRMS THE PATTERN GENERALIZES TO NEW METHODS
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This chapter's own get_cart() already survived a simulated restart.
This exercise confirms a BRAND NEW method, added after the fact,
automatically inherits the same property - not because
get_item_count() does anything special, but because nothing about
StatelessCartService's own design depends on server memory in the
first place. Any method written the same way (taking the relevant
state as a parameter, rather than reading it from self) gets
restart-survival for free.

WHY THIS WORKS AS AN ANSWER
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The new method follows this chapter's own established stateless shape
exactly, and it's verified working correctly against a genuinely fresh
service instance - the same restart-simulation technique this chapter
used for get_cart() - rather than only assumed to inherit the
property.