code: def dixon_price(theta):
      
      x, y = theta
      obj = (x - 1) ** 2 + 2 * (2 * y ** 2 - x) ** 2
      grad = np.array([
          2 * x - 2 - 4 * (2 * y ** 2 - x),
          16 * (2 * y ** 2 - x) * y,
      ])
      return obj, grad
docs: Dixon-Price function