input: Write a python function to find the highest product of any two numbers in a list.
  assert highest_product([4, -2, 10, 8, 9]) == 90
  assert highest_product([1, 2, 3, 4, 5]) == 20
  assert highest_product([-10, -20, 5, 3, 2]) == 200
output: def highest_product(lst):
      lst.sort()
      return max(lst[-1] * lst[-2], lst[0] * lst[1])