+def population_counts(lst: List[Any]) -> Mapping[Any, int]:
+ """
+ Return a population count mapping for the list (i.e. the keys are
+ list items and the values are the number of occurrances of that
+ list item in the original list.
+
+ >>> population_counts([1, 1, 1, 2, 2, 3, 3, 3, 4])
+ Counter({1: 3, 3: 3, 2: 2, 4: 1})
+
+ """
+ return Counter(lst)
+
+
+def most_common_item(lst: List[Any]) -> Any:
+
+ """
+ Return the most common item in the list. In the case of ties,
+ which most common item is returned will be random.
+
+ >>> most_common_item([1, 1, 1, 2, 2, 3, 3, 3, 3, 4, 4])
+ 3
+
+ """
+ return population_counts(lst).most_common(1)[0][0]
+
+
+def least_common_item(lst: List[Any]) -> Any:
+ """
+ Return the least common item in the list. In the case of
+ ties, which least common item is returned will be random.
+
+ >>> least_common_item([1, 1, 1, 2, 2, 3, 3, 3, 4])
+ 4
+
+ """
+ return population_counts(lst).most_common()[-1][0]
+
+
+def dedup_list(lst: List[Any]) -> List[Any]:
+ """
+ Remove duplicates from the list performantly.
+
+ >>> dedup_list([1, 2, 1, 3, 3, 4, 2, 3, 4, 5, 1])
+ [1, 2, 3, 4, 5]
+
+ """
+ return list(set(lst))
+
+