input: Write a function to generate a list by picking every second item from a provided list.
  assert alternate_elements(["red", "black", "white", "green", "orange"])==['red', 'white', 'orange']
  assert alternate_elements([2, 0, 3, 4, 0, 2, 8, 3, 4, 2])==[2, 3, 0, 8, 4]
  assert alternate_elements([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])==[1, 3, 5, 7, 9]
output: def alternate_elements(lst):
      return lst[::2]