Given an orders DataFrame with customer_id and amount_usd, return one row per customer with: - n_orders — number of orders - total_usd — sum of amount_usd
An order with a missing amount_usd still counts as an order (it adds nothing to the total). Rows with a missing customer_id belong to no customer and are left out.
customer_id must be a normal column (not the index). Any row order.
What the tests check
3 on Run · 4 on Submit01counts and sums per customer
02customer_id is a column, not the index
03an order with a missing amount still counts as an order
Submit runs these and one more check you don’t see, so code written for the visible tests alone can still miss.