title: LightGBMError: Do not support special JSON characters in feature name - The same code is working in jupyter but doesn't work in Spyder
body: <p>I have the following code:</p>
  
  <pre><code>    most_important = features_importance_chi(importance_score_tresh, 
      df_user.drop(columns = 'CHURN'),churn)
      X = df_user.drop(columns = 'CHURN')
      churn[churn==2] = 1
      y = churn
  
      # handle undersample problem
      X,y = handle_undersampe(X,y)
  
      # train the model
  
      X=X.loc[:,X.columns.isin(most_important)].values
      y=y.values
  
      parameters = {
      'application': 'binary',
      'objective': 'binary',
      'metric': 'auc',
      'is_unbalance': 'true',
      'boosting': 'gbdt',
      'num_leaves': 31,
      'feature_fraction': 0.5,
      'bagging_fraction': 0.5,
      'bagging_freq': 20,
      'learning_rate': 0.05,
      'verbose': 0
      }
  
      # split data
      x_train, x_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42, stratify=y)
  
      train_data = lightgbm.Dataset(x_train, label=y_train)
      test_data = lightgbm.Dataset(x_test, label=y_test)
      model = lightgbm.train(parameters,
                         train_data,
                         valid_sets=[train_data, test_data], 
                         **feature_name=most_important,**
                         num_boost_round=5000,
                         early_stopping_rounds=100) 
  </code></pre>
  
  <p>and function which returns most_important parameter</p>
  
  <pre><code>def features_importance_chi(importance_score_tresh, X, Y):
      model = ExtraTreesClassifier(n_estimators=10)
      model.fit(X,Y.values.ravel())
      feature_list = pd.Series(model.feature_importances_,
                               index=X.columns)
      feature_list = feature_list[feature_list &gt; importance_score_tresh]
      feature_list = feature_list.index.values.tolist()
      return feature_list
  </code></pre>
  
  <p>Funny thing is that this code in Spyder returns the following error</p>
  
  <p><code>LightGBMError: Do not support special JSON characters in feature name.</code> </p>
  
  <p>but in jupyter works fine. I am able to print the list of most important features.</p>
  
  <p>Any idea what could be the reason for this error?</p>