回测时，kline数据不正确

回测kline序列中，第一个数据是正确的，之后的数据全都不准确，换个合约也还是一样。用这样的数据来计算出的策略肯定回测数据有很大的问题，望尽快修正这个bug

！！！！但是在web图表中渲染出的k线是准确的

klines = api.get_kline_serial("SHFE.ni2106", 60, 100)
print(klines.iloc[-1])

第一个数据：

datetime 1617346740000000000.0
id 89250.0
open 123480.0
high 123520.0
low 123410.0
close 123470.0
volume 2431.0
open_oi 144798.0
close_oi 144090.0
symbol SHFE.ni2106
duration 60
Name: 99, dtype: object

之后的数据中open、hight、low、close的数据都一样，open_oi和close_oi的值也一样

datetime 1617670800000000000.0
id 89251.0
open 123460.0
high 123460.0
low 123460.0
close 123460.0
volume 0.0
open_oi 144090.0
close_oi 144090.0
symbol SHFE.ni2106
duration 60
diff NaN
diff.board None
diff.color None
dea NaN
dea.board None
dea.color None
Name: 99, dtype: object

datetime 1617670860000000000.0
id 89252.0
open 125060.0
high 125060.0
low 125060.0
close 125060.0
volume 0.0
open_oi 146974.0
close_oi 146974.0
symbol SHFE.ni2106
duration 60
diff NaN
diff.board None
diff.color None
dea NaN
dea.board None
dea.color None
Name: 99, dtype: object

web图表中渲染出的k线