这段代码哪里有问题我导入了所有库，但它不起作用。
from tensorflow.keras.preprocessing.sequence import pad_sequences
from keras.utils.data_utils import pad_sequences
max_len = 200
X_train = keras.preprocessing.sequence.pad_sequences(X_train, maxlen = maxlen)
X_test = sequence.pad_sequence(X_test, max_len = maxlen)
y_test = np.array(y_test)
y_train = np.array(y_train)