Fix missing import

sklearn_validation.py

@@ -12,8 +12,13 @@ import sys
 import numpy as np
 import pandas as pd
 from sklearn import preprocessing, svm
-from sklearn.metrics import (accuracy_score, make_scorer, matthews_corrcoef,
-                             roc_auc_score)
+from sklearn.ensemble import RandomForestClassifier
+from sklearn.metrics import (
+    accuracy_score,
+    make_scorer,
+    matthews_corrcoef,
+    roc_auc_score,
+)
 from sklearn.model_selection import GridSearchCV, StratifiedShuffleSplit
 from sklearn.pipeline import Pipeline