input: Write a python function to calculate the dot product of two vectors.
  assert dot_product([1, 2, 3], [2, 3, 4]) == 20
  assert dot_product([1, 0, -1], [-1, 0, 1]) == -2
  assert dot_product([1, 2], [3, 4]) == 11
output: def dot_product(vector1, vector2):
      return sum(a * b for a, b in zip(vector1, vector2))