Fix tree_sort dropping duplicate values

@@ -36,11 +36,11 @@ def insert(self, val: T) -> None:                 self.left = Node(val)             else:                 self.left.insert(val)-        elif val > self.val:-            if self.right is None:-                self.right = Node(val)-            else:-                self.right.insert(val)+        # Equal values go to the right so that duplicates are kept.+        elif self.right is None:+            self.right = Node(val)+        else:+            self.right.insert(val)   def tree_sort[T: Comparable](arr: Iterable[T]) -> tuple[T, ...]:@@ -63,6 +63,10 @@ def tree_sort[T: Comparable](arr: Iterable[T]) -> tuple[T, ...]:     ('a', 'b', 'c')     >>> tree_sort([2.5, -1, 0.0])     (-1, 0.0, 2.5)+    >>> tree_sort([3, 1, 3, 2, 1])+    (1, 1, 2, 3, 3)+    >>> tree_sort([2, 2, 2])+    (2, 2, 2)     >>> tree_sort([1, "a"])     Traceback (most recent call last):         ...