[MNT] remove import conditionals for python 3.6 (#1928)

removes import conditionals for `python 3.6` - 3.6 has been deprecated
for years now.

Author: fkiraly

tests/test_models/test_temporal_fusion_transformer.py

@@ -1,3 +1,4 @@
+from contextlib import nullcontext
 import pickle
 import shutil
 import sys
@@ -8,6 +9,7 @@
 import numpy as np
 import pandas as pd
 import pytest
+from test_models.conftest import make_dataloaders
 import torch
 
 from pytorch_forecasting import Baseline, TimeSeriesDataSet
@@ -29,18 +31,6 @@
 )
 from pytorch_forecasting.utils._dependencies import _get_installed_packages
 
-if sys.version.startswith("3.6"):  # python 3.6 does not have nullcontext
-    from contextlib import contextmanager
-
-    @contextmanager
-    def nullcontext(enter_result=None):
-        yield enter_result
-
-else:
-    from contextlib import nullcontext
-
-from test_models.conftest import make_dataloaders
-
 
 def test_integration(multiple_dataloaders_with_covariates, tmp_path):
     _integration(