title: split() missing 1 required positional argument: 'y'
body: <p>I'm trying to predict the Viscosity of plastic fluid, I used  Random Forest Regressor and K-Fold cross-validation to train my data.</p>
  
  <pre><code>RFR = RandomForestRegressor(n_estimators = 2000,max_depth = 20, n_jobs=-1, random_state = 0)
  
  scores = []
  Kfold = StratifiedKFold(n_splits=10, random_state = 0, shuffle=True)
  
  for i in range(10):
      result = next(Kfold.split(X_train), None)
      input_train = df.iloc[result[0]]
      input_test = df.iloc[result[1]]
      output_train = y.iloc[result[0]]
      output_test = y.iloc[result[1]]
      model = RFR.fit(input_train,output_train)
      predictions = RFR.predict(input_test)
      scores.append(model.score(input_test,output_test))
  print('Scores from each Iteration: ', scores)
  print('Average K-Fold Score :' , np.mean(scores))
  </code></pre>
  
  <p>I want ta train my model for 10 fold cross-validation, but I got this error message :</p>
  
  <pre><code>TypeError: split() missing 1 required positional argument: 'y'
  </code></pre>