como implementar métricas personalizadas em keras?

Eu recebo este erro:

sum () obteve um argumento inesperado da palavra-chave 'out'

quando eu executo esse código:

import pandas as pd, numpy as np
import keras
from keras.layers.core import Dense, Activation
from keras.models import Sequential

def AUC(y_true,y_pred):
    not_y_pred=np.logical_not(y_pred)
    y_int1=y_true*y_pred
    y_int0=np.logical_not(y_true)*not_y_pred
    TP=np.sum(y_pred*y_int1)
    FP=np.sum(y_pred)-TP
    TN=np.sum(not_y_pred*y_int0)
    FN=np.sum(not_y_pred)-TN
    TPR=np.float(TP)/(TP+FN)
    FPR=np.float(FP)/(FP+TN)
    return((1+TPR-FPR)/2)

# Input datasets

train_df = pd.DataFrame(np.random.rand(91,1000))
train_df.iloc[:,-2]=(train_df.iloc[:,-2]>0.8)*1


model = Sequential()
model.add(Dense(output_dim=60, input_dim=91, init="glorot_uniform"))
model.add(Activation("sigmoid"))
model.add(Dense(output_dim=1, input_dim=60, init="glorot_uniform"))
model.add(Activation("sigmoid"))

model.compile(optimizer='rmsprop',loss='binary_crossentropy',metrics=[AUC])


train_df.iloc[:,-1]=np.ones(train_df.shape[0]) #bias
X=train_df.iloc[:,:-1].values
Y=train_df.iloc[:,-1].values
print X.shape,Y.shape

model.fit(X, Y, batch_size=50,show_accuracy = False, verbose = 1)

É possível implementar uma métrica personalizada além de fazer um loop em lotes e editar o código-fonte?

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