债券凸性

def solve(____):
    coupon = face_value * coupon_rate
    price = sum(coupon / (____ + ytm) ** t for t in range(____, maturity + ____))
    price += face_value / (____ + ytm) ** maturity
    convexity = sum(t * (____) * coupon / (____ + ytm) ** (____) for t in range(____, maturity + ____))
    convexity += maturity * (____) * face_value / (____ + ytm) ** (____)
    convexity = convexity / price
    return {"____": round(____), "____": round(____)}