input: Write a python function to calculate the dot product of two lists of the same length.
  assert dot_product([1, 2, 3], [4, 5, 6]) == 32
  assert dot_product([0, 0, 0], [1, 2, 3]) == 0
  assert dot_product([1, -2, 3], [-4, 5, -6]) == -28
output: def dot_product(list1, list2):
      return sum(x * y for x, y in zip(list1, list2))