input: Write a python function to calculate the dot product of two vectors using the provided Vector class.
  assert Vector(1, 2, 3).dot(Vector(4, 5, 6)) == 32
  assert Vector(0, 0, 0).dot(Vector(1, 2, 3)) == 0
  assert Vector(1, -1, 1).dot(Vector(-1, 1, -1)) == -3
output: class Vector:
      def __init__(self, x, y, z):
          self.x = x
          self.y = y
          self.z = z
  
      def dot(self, other):
          return self.x * other.x + self.y * other.y + self.z * other.z