fix: Resolve 4 pylint errors

- Fix function-redefined in test_groupby_regression.py
- Add LinAlgError import in groupby_regression_optimized.py
- Fix import paths in sliding window test files

Author: miranov25

UTILS/dfextensions/groupby_regression/groupby_regression_optimized.py

@@ -413,6 +413,8 @@ def make_parallel_fit_v2(
 # ======================================================================
 
 import numpy as np
+from numpy.linalg import LinAlgError
+from numpy.linalg import LinAlgError
 import pandas as pd
 import time
 

UTILS/dfextensions/groupby_regression/tests/test_groupby_regression.py

@@ -290,7 +290,7 @@ def test_sigma_cut_impact():
 
 
 
-def test_make_parallel_fit_robust(sample_data):
+def test_make_parallel_fit_robust_v2(sample_data):
     df = sample_data.copy()
     df_out, dfGB = GroupByRegressor.make_parallel_fit(
         df,

UTILS/dfextensions/groupby_regression/tests/test_groupby_regression_sliding_window.py

@@ -779,7 +779,7 @@ def test_window_size_zero_parity_with_v4_relaxed():
       Establishes continuity with v4 when sliding window is disabled.
     """
     try:
-        from ..groupby_regression_optimized import make_parallel_fit as make_parallel_fit_v4
+        from ..groupby_regression import make_parallel_fit as make_parallel_fit_v4
     except Exception:
         pytest.skip("v4 not available for comparison")
 

UTILS/dfextensions/groupby_regression/tests/test_groupby_regression_sliding_window_verbose.py

@@ -849,7 +849,7 @@ def test_window_size_zero_parity_with_v4_relaxed():
       Establishes continuity with v4 when sliding window is disabled.
     """
     try:
-        from ..groupby_regression_optimized import make_parallel_fit as make_parallel_fit_v4
+        from ..groupby_regression import make_parallel_fit as make_parallel_fit_v4
     except Exception:
         pytest.skip("v4 not available for comparison")