` if df is not None:
for ix, row in df.iterrows():
bar = BarData(
symbol=symbol,
exchange=exchange,
interval=interval,
datetime=row.name.to_pydatetime() - adjustment,
open_price=row["open"],
high_price=row["high"],
low_price=row["low"],
close_price=row["close"],
volume=row["volume"],
gateway_name="RQ"
)
data.append(bar)
return data
`
adjustment 的作用是什么?如果调整的话实际数据点位和时间不对应了啊,不明白,求解释?