def reinitializable_input_fn(filenames, labels, train_val_ratio=0.8):
    num_files = len(filenames)
    num_train_files = int(num_files * train_val_ratio)
    train_filenames = filenames[:num_train_files]
    train_labels = labels[:num_train_files]
    val_filenames = filenames[num_train_files:]
    val_labels = labels[num_train_files:]

    train_data = tf.data.Dataset.from_tensor_slices(
        (train_filenames, train_labels))
    train_data = train_data.map(_parse_data).shuffle(1000).repeat().batch(4)

    val_data = tf.data.Dataset.from_tensor_slices(
        (val_filenames, val_labels))
    val_data = val_data.map(_parse_data).batch(1)
    iterator = tf.data.Iterator.from_structure(train_data.output_types,
                                               train_data.output_shapes)

    next_element = iterator.get_next()

    train_init_op = iterator.make_initializer(train_data)
    val_init_op = iterator.make_initializer(val_data)

    return next_element, train_init_op, val_init_op