input: Write a python function to check if a number is in a list and return its index if found, otherwise return False.
  assert is_in_linear_list([2, 3, 5, 6, 8, 9], 5) == "Found at 2 position"
  assert is_in_linear_list([2, 3, 5, 6, 8, 9], 7) == False
  assert is_in_linear_list([1, 4, 6, 7, 8], 4) == "Found at 1 position"
output: def is_in_linear_list(lst, num):
      for index, value in enumerate(lst):
          if value == num:
              return f"Found at {index} position"
      return False