input: Write a function to sort a list of tuples by the second item.
  assert sort_tuple([("b", 0), ("a", 1), ("c", -1)]) == [("c", -1), ("b", 0), ("a", 1)]
  assert sort_tuple([(2, 3), (1, 2), (3, 1)]) == [(3, 1), (1, 2), (2, 3)]
  assert sort_tuple([("apple", 10), ("banana", 5), ("cherry", 15)]) == [("banana", 5), ("apple", 10), ("cherry", 15)]
output: def sort_tuple(lst):
      return sorted(lst, key=lambda x: x[1])