bug：单标的数据维度不对

[quant2008]

`from alphagen.data.expression import *
from alphagen_generic.features import *
import torch

if name == "main":

# device = torch.device('cuda:0')
device=torch.device('cpu')

data = StockData(instrument=["SH600038"], start_time="2021-01-01", end_time="2023-06-30", max_backtrack_days=0,max_future_days=0, device=device)
print(data.make_dataframe(data._get_data()[0]))`

运行如上代码出如下错误，如果设置参数instrument=“csi300”，则结果正确。看样子对设置单一标的，数据维度不对：
[22432:MainThread](2023-12-29 16:34:42,113) ERROR - qlib.workflow - [utils.py:41] - An exception has been raised[ValueError: number of stocks in the provided tensor (6) doesn't match that of the current StockData (1)].
File "e:/myquant/alphagen-master/test2.py", line 16, in
print(data.make_dataframe(data._get_data()[0]))
File "e:\myquant\alphagen-master\alphagen_qlib\stock_data.py", line 121, in make_dataframe
raise ValueError(f"number of stocks in the provided tensor ({n_stocks}) doesn't "
ValueError: number of stocks in the provided tensor (6) doesn't match that of the current StockData (1)