Full code

import keras
from keras.models import Sequential
from keras.layers import Dense

def build_classifier():
    classifier = Sequential()
    classifier.add(Dense(units=6, kernel_initializer='uniform', activation='relu', input_dim=11))
    classifier.add(Dense(units=6, kernel_initializer='uniform', activation='relu'))
    classifier.add(Dense(units=1, kernel_initializer='uniform', activation='sigmoid'))
    classifier.compile(optimizer='adam', loss='binary_crossentropy', metrics=['accuracy'])
    return classifier

from keras.wrappers.scikit_learn import KerasClassifier
from sklearn.model_selection import cross_val_score

classifier = KerasClassifier(build_fn = build_classifier, batch_size=10, nb_epoch=100)
accuracies = cross_val_score(estimator = classifier, X=X_train,y=y_train, cv=10, n_jobs=-1)
mean = accuracies.mean()