new_contents: from keras.models import Sequential
  from keras.layers import Dense, Activation
  from keras.optimizers import SGD
  
  # simple xor example
  x = [[1,1],[1,0],[0,1],[0,0]]
  y = [0, 1, 1, 0]
  
  # build model with 1 hidden layer 4 neuron
  model = Sequential()
  model.add(Dense(output_dim=4, input_dim=2))
  model.add(Activation("tanh"))
  model.add(Dense(output_dim=1))
  model.add(Activation("sigmoid"))
  
  #change the default learning_rate
  sgd = SGD(lr=0.05)
  model.compile(loss='binary_crossentropy', optimizer=sgd, metrics=['accuracy'])
  
  model.fit(x, y, nb_epoch=300, batch_size=4)
  
  loss = model.evaluate(x, y, batch_size=4)
  classes = model.predict_classes(x, batch_size=4)
  
  print loss
  print classes
subject: add Keras for XOR problem