AttributeError: 'zipline.assets._assets.Equity' object has no attribute 'history'

import talib
import pandas

# ---------------------------------------------------
n1, n2, period, stock = 10, 21, 12, sid(24)
# ---------------------------------------------------
def initialize(context):
    schedule_function(open_positions, date_rules.week_start(), time_rules.market_open())

def handle_data(context, data):
    if get_open_orders(): return
    close = stock.history(stock, 'close', period + 1, '1d')
    low = stock.history(stock, 'low', period + 1, '1d')
    high = stock.history(stock, 'high', period + 1, '1d')
    ap = (high+low+close)/3
    esa = talib.EMA(ap, timeperiod=n1)
    d = talib.EMA(abs(ap - esa), timeperiod=n1)
    ci = (ap - esa) / (0.015 * d)
    wt1 = talib.EMA(ci, timeperiod=n2)
    wt1 = wt1.dropna()
    wt2 = talib.SMA(wt1, timeperiod=4)
    wt2 = wt2.dropna()

def open_positions(context, data):
    if data.can_trade(stock <  wt1):
        order_target_percent(stock, 2)
    elif data.can_trade(stock > wt2):
        order_target_percent(stock, -1)