input: Write a python function to add and subtract two vectors.
  assert (v1 + v2).x == 6 and (v1 + v2).y == 10
  assert (v1 - v2).x == -2 and (v1 - v2).y == -2
  v5 = Vector(0, 0)
  v6 = Vector(3, -3)
  assert (v5 + v6).x == 3 and (v5 + v6).y == -3
  assert (v5 - v6).x == -3 and (v5 - v6).y == 3
output: class Vector:
      def __init__(self, x, y):
          self.x = x
          self.y = y
  
      def __add__(self, other):
          return Vector(self.x + other.x, self.y + other.y)
  
      def __sub__(self, other):
          return Vector(self.x - other.x, self.y - other.y)
  
  # Example vectors for testing
  v1 = Vector(2, 4)
  v2 = Vector(4, 6)