input: Write a python function to find the first occurrence of a target value in a list.
  assert find_first_occurrence([1, 7, 3, 5, 4, 7, 8, 10, 6, 9], 7) == 1
  assert find_first_occurrence([10, 20, 30, 40, 50], 30) == 2
  assert find_first_occurrence([5, 4, 3, 2, 1], 6) == -1
output: def find_first_occurrence(lst, target):
      try:
          return lst.index(target)
      except ValueError:
          return -1