Suppose that a DataFrame called subscriptions stores information about the active Hyperskill subscriptions. In particular, the day, month, and year when a subscription started are stored in the day, month and year columns respectively:
day month year
0 12 10 2022
1 15 11 2022
2 8 11 2022
3 21 10 2022
4 23 12 2022
5 9 12 2022
Create a new column called start_date that would store the subscription date as a single pandas datetime object. Print the resulting DataFrame.