input: Write a python function to implement linear search algorithm in a list and return the index of the target value or -1 if the target value is not found.
  assert linear_search([1, 2, 3, 4, 5], 3) == 2
  assert linear_search([10, 20, 30, 40, 50], 25) == -1
  assert linear_search([7, 8, 9, 10], 10) == 3
output: def linear_search(lst, target):
      for index, value in enumerate(lst):
          if value == target:
              return index
      return -1