import tensorflow as tf

from sklearn.metrics import roc_auc_score

import numpy as np

###########  classification ##############

def cross_entropy(y_true, y_pred):

    cost = tf.nn.sigmoid_cross_entropy_with_logits(labels=labels, logits=logits)

    return cost

def weighted_cross_entropy(y_true, y_pred, pos_weight):

    cost = tf.nn.weighted_cross_entropy_with_logits(labels=labels, logits=logits, 

                                                    pos_weight = pos_weight)

    return cost

def MALE(y_obs, y_pred):

    return tf.keras.backend.log(0.5 + tf.keras.backend.abs(y_pred - y_obs))