def contains_only_zeros(image_data):
    """
    Determines if data patch should be omitted from AL training. Patches in the
    border region of the image can contain only padding (only values of 0). This
    messes with the AL query strategy because the model is very uncertain, but
    the patches don't contribute to training because they contain no real data.
    :param image_data: numpy array with image data
    :return: boolean value, True if image_data contains only 0, False otherwise
    """
    non_zero_values = image_data[image_data != 0]
    return (non_zero_values.size == 0)