def METHOD_NAME(x, y):
    dy_xx = dde.grad.hessian(y, x, i=0, j=0)
    dy_yy = dde.grad.hessian(y, x, i=1, j=1)
    f = (d - 1) * k0**2 * sin(k0 * x[:, 0:1]) * sin(k0 * x[:, 1:2])
    return -dy_xx - dy_yy - k0**2 * y - f