IndexError：只有整数，切片（`：`），省略号（```），numpy.newaxis（`None`）和整数或布尔数组是使用skfeature的有效索引

Question

select = json.dumps(c.fetchone()[0])

运行此代码时，它会抛出以下错误：

from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.datasets import fetch_20newsgroups
from skfeature.function.statistical_based import gini_index
import numpy as np

tfidf_vectorizer = TfidfVectorizer(stop_words='english')
categories=['alt.atheism','comp.graphics','comp.os.ms-windows.misc',
        'comp.sys.ibm.pc.hardware','comp.sys.mac.hardware',
        'comp.windows.x','misc.forsale','rec.autos','rec.motorcycles',
        'rec.sport.baseball']

data_train = fetch_20newsgroups(subset='train', categories=categories,
                            shuffle=True, random_state=42)

data_test = fetch_20newsgroups(subset='test', categories=categories,
                           shuffle=True, random_state=42)
# split a training set and a test set
y_train, y_test = data_train.target, data_test.target
vectorizer = TfidfVectorizer(stop_words='english')
X_train = vectorizer.fit_transform(data_train.data)
X_test = vectorizer.transform(data_test.data)

feature_names = vectorizer.get_feature_names()

score = gini_index.gini_index(X_train, y_train)
ranking= gini_index.feature_ranking(score)