fix gat dataset

Author: you-n-g

qlib/contrib/model/pytorch_gats_ts.py

@@ -27,10 +27,9 @@
 
 class DailyBatchSampler(Sampler):
     def __init__(self, data_source):
-
         self.data_source = data_source
-        self.data = self.data_source.data.loc[self.data_source.get_index()]
-        self.daily_count = self.data.groupby(level=0).size().values  # calculate number of samples in each batch
+        # calculate number of samples in each batch
+        self.daily_count = pd.Series(index=self.data_source.get_index()).groupby('datetime').size().values
         self.daily_index = np.roll(np.cumsum(self.daily_count), 1)  # calculate begin index of each batch
         self.daily_index[0] = 0