input: Write a python function to sort a list of tuples based on the second element in each tuple.
  assert sort_by_tuple_second([(1, 3), (3, 2), (5, 1)]) == [(5, 1), (3, 2), (1, 3)]
  assert sort_by_tuple_second([(4, 4), (1, 1), (2, 3), (3, 2)]) == [(1, 1), (3, 2), (2, 3), (4, 4)]
  assert sort_by_tuple_second([(9, 5), (7, 7), (8, 6), (5, 5)]) == [(9, 5), (5, 5), (8, 6), (7, 7)]
output: def sort_by_tuple_second(lst):
      return sorted(lst, key=lambda x: x[1])