input: Write a python function to multiply each element of a list by the next element in the list, and for the last element multiply it by 1.
  assert multiply_by_next([1, 2, 3, 4, 5]) == [2, 6, 12, 20, 5]
  assert multiply_by_next([3, 6, 9, 12]) == [18, 54, 108, 12]
  assert multiply_by_next([2, 4, 6]) == [8, 24, 6]
output: def multiply_by_next(lst):
      result = []
      for i in range(len(lst)):
          if i < len(lst) - 1:
              result.append(lst[i] * lst[i + 1])
          else:
              result.append(lst[i] * 1)
      return result