The function address_to_string consumes an Address and produces a string representation of its fields.

An Address has a number (integer), street (string), city (string), and state (string).

The string representation should combine the number and street with a space, the city and state with a comma and a space, and then a newline between those two parts.

So the Address(18, "Amstel Ave", "Newark", "DE") would become "18 Amstel Ave\nNewark, DE"