请写出股票交易的类、核心函数及其量化交易代码

类：股票、交易账户、市场、股票交易者、策略、订单等。

核心函数：买入、卖出、查询持仓、查询账户资金、查询市场行情、撤销订单等。

量化交易代码：

import akshare as ak

# 获取股票市场行情
stock_market = ak.stock_zh_a_spot()
# 获取交易账户信息
account_info = {"balance": 10000, "stocks": {}}

# 定义买入函数
def buy(stock_code, amount):
    price = stock_market.loc[stock_market["证券代码"] == stock_code, "现价"].values[0]
    cost = price * amount
    if cost > account_info["balance"]:
        print("余额不足，买入失败！")
        return
    if stock_code not in account_info["stocks"]:
        account_info["stocks"][stock_code] = 0
    account_info["stocks"][stock_code] += amount
    account_info["balance"] -= cost
    print(f"买入{stock_code}{amount}股成功！")

# 定义卖出函数
def sell(stock_code, amount):
    if stock_code not in account_info["stocks"]:
        print("持仓中没有该股票，卖出失败！")
        return
    if amount > account_info["stocks"][stock_code]:
        print("持仓不足，卖出失败！")
        return
    price = stock_market.loc[stock_market["证券代码"] == stock_code, "现价"].values[0]
    income = price * amount
    account_info["stocks"][stock_code] -= amount
    account_info["balance"] += income
    print(f"卖出{stock_code}{amount}股成功！")

# 调用买入函数
buy("600519", 10)
# 调用卖出函数
sell("600519", 5)

# 查询持仓
for stock_code, amount in account_info["stocks"].items():
    print(f"{stock_code}: {amount}股")

# 查询账户资金余额
print(f"账户余额：{account_info['balance']}元")