We want to create a structure that will represent a deck of cards (not necessarily full). Each card has a character (between '2' to '9' and 'T', 'J', 'Q', 'K', 'A') and a suit (diamonds, hearts, clubs, spades):
a) Choose a representation for each card and also for the deck of cards (it can be empty or non-empty)
b) Define an add_card predicate that takes a card and a deck and adds the card if it is not already there (i.e. no duplicates) creating a new deck of cards. If the card is not of a valid suit or number this predicate will simply do nothing.