[ci][python] apply isort to examples/python-guide/sklearn_example.py #3958 (#3965)

examples/python-guide/sklearn_example.py

@@ -1,11 +1,11 @@
 # coding: utf-8
 import numpy as np
 import pandas as pd
-import lightgbm as lgb
-
 from sklearn.metrics import mean_squared_error
 from sklearn.model_selection import GridSearchCV
 
+import lightgbm as lgb
+
 print('Loading data...')
 # load or create your dataset
 df_train = pd.read_csv('../regression/regression.train', header=None, sep='\t')