serving_input_fn.py

def serving_input_fn():
    # Note: only handles one image at a time 
    feature_placeholders = {'image_bytes': 
                            tf.placeholder(tf.string, shape=())}
    image, _ = read_and_preprocess(
        tf.squeeze(feature_placeholders['image_bytes']))
    features = {
      'image': tf.expand_dims(image, 0)
    }
    return tf.estimator.export.ServingInputReceiver(features, feature_placeholders)