input: Write a python function to find the index of a target element in a list.
  assert search_index([5, 7, 8, 6], 8) == 2
  assert search_index([1, 2, 3, 4, 5], 3) == 2
  assert search_index([10, 20, 30, 40], 25) == -1
output: def search_index(lst, target):
      try:
          return lst.index(target)
      except ValueError:
          return -1