Given a list of transactions, How can we calculate the frequency counts of all possible item-sets? For example, Input: ID Purchased Items 1 apple, banana, lemon 2 banana, berry, lemon, orange 3 banana, berry, lemon Output: Itemset Frequency apple, banana 1 apple, lemon 1 banana, berry 2 banana, lemon 3 ... apple, banana, lemon 1 banana, berry, lemon 2 ... banana, berry, lemon, orange 1