fix pytest error

Author: SunsetWolf

.github/workflows/test_qlib_from_source_slow.yml

@@ -69,4 +69,4 @@ jobs:
         max_attempts: 3
         command: |
           cd tests
-          python -m pytest . -m "slow" --durations=0
+          python -m pytest -s . -m "slow" --durations=0

tests/data_mid_layer_tests/test_dataloader.py

@@ -11,12 +11,16 @@
 from qlib.data.dataset.handler import DataHandlerLP
 from qlib.contrib.data.loader import Alpha158DL, Alpha360DL
 from qlib.data import D
+import logging
+
+logging.basicConfig(level=logging.INFO)
 
 
 class TestDataLoader(unittest.TestCase):
 
     def test_nested_data_loader(self):
-        qlib.init()
+        print("debug info\n")
+        qlib.init(kernels=1)
         nd = NestedDataLoader(
             dataloader_l=[
                 {
@@ -30,7 +34,7 @@ def test_nested_data_loader(self):
         )
         # Of course you can use StaticDataLoader
 
-        dataset = nd.load()
+        dataset = nd.load(start_time="2020-01-01", end_time="2020-01-31")
 
         assert dataset is not None