input: Write a python function to find the last occurrence of an element in a list.
  assert last_occurrence(5, [1, 2, 5, 3, 5, 4]) == 4
  assert last_occurrence(7, [7, 3, 7, 4, 7]) == 4
  assert last_occurrence(2, [1, 2, 3, 4, 2, 5]) == 4
  assert last_occurrence(10, [1, 2, 3, 4, 5]) == -1
output: def last_occurrence(element, lst):
      for i in range(len(lst) - 1, -1, -1):
          if lst[i] == element:
              return i
      return -1