estimators_blog_model_head.py

head = tf.contrib.estimator.binary_classification_head()
optimizer = tf.train.AdamOptimizer()    
def _train_op_fn(loss):
    tf.summary.scalar('loss', loss)
    return optimizer.minimize(
        loss=loss,
        global_step=tf.train.get_global_step())

return head.create_estimator_spec(
    features=features,
    labels=labels,
    mode=mode,
    logits=logits,
    train_op_fn=_train_op_fn)