input: Write a python function to sort a list of tuples based on the second element in each tuple.
  assert sort_tuples_by_second([(1, 3), (2, 1), (4, 2)]) == [(2, 1), (4, 2), (1, 3)]
  assert sort_tuples_by_second([(5, 5), (1, 1), (3, 3)]) == [(1, 1), (3, 3), (5, 5)]
  assert sort_tuples_by_second([(10, 2), (8, 5), (6, 4)]) == [(10, 2), (6, 4), (8, 5)]
output: def sort_tuples_by_second(lst):
      return sorted(lst, key=lambda x: x[1])