Stock Report

Write the whole Inventory class. The constructor creates an empty dict attribute stock from item name to quantity; add(item, quantity) tops up an existing key or creates it; total_items() loops over the keys and returns the sum of every quantity; report() prints one line per item as <item>: <quantity> in alphabetical order, looping over sorted(self.stock). Do NOT write a main block or any top-level test code; the tests construct the class. Input: two lines, an item name and a whole-number quantity, which the tests pass to add on an inventory already holding 3 apples and 5 pears; the tests then call report and print the total.