在学习莫烦教程中keras教程时，报错：TypeError: to_categorical() got an unexpected keyword argument 'nb_classes'，代码如下
X_train = X_train.reshape(X_train.shape[0],-1) / 255 #normalize
X_test = X_test.reshape(X_test.shape[0],-1) / 255 #normalize
y_train = np_utils.to_categorical(y_train, nb_classes=10)
y_test = np_utils.to_categorical(y_test, nb_classes=10)
错误原因：keras版本问题，将nb_classes改为num_classes
参考keras文档：http://keras-cn.readthedocs.io/en/latest/utils/