input: Write a python function to find the index of the first occurrence of an element in a list.
  assert find_index([1, 2, 3, 4, 5], 3) == 2
  assert find_index([10, 20, 30, 40, 50], 40) == 3
  assert find_index([5, 10, 15, 20, 25], 5) == 0
output: def find_index(lst, element):
      for index, value in enumerate(lst):
          if value == element:
              return index
      return -1