unhashable type 27set 27 python

1fruits = {
2        "Citrus": {
3             {"oranges", "grapefruits", "mandarins", "limes"}
4    },
5        "Stone fruit": {
6             {"ectarines", "apricots", "peaches", "plums"}
7    },
8        "Tropical and exotic": {
9             {"bananas", "mangoes"},
10    },
11        "Berries": {
12             {"strawberries", "raspberries", "blueberries", "kiwifruit", "passionfruit"},
13    },
14        "Melons": {
15             {"watermelons", "rockmelons", "honeydew melons"}
16    },
17        "Other": {
18            {"Apples", "Pears", "Tomatoes", "Avocados"}
19    }
20}