How to use the imgtool.image.DEP_IMAGES_KEY function in imgtool

images = re.findall(r"\((\d+)", value)
        if len(images) == 0:
            raise click.BadParameter(
                "Image dependency format is invalid: {}".format(value))
        raw_versions = re.findall(r",\s*([0-9.+]+)\)", value)
        if len(images) != len(raw_versions):
            raise click.BadParameter(
                '''There's a mismatch between the number of dependency images
                and versions in: {}'''.format(value))
        for raw_version in raw_versions:
            try:
                versions.append(decode_version(raw_version))
            except ValueError as e:
                raise click.BadParameter("{}".format(e))
        dependencies = dict()
        dependencies[image.DEP_IMAGES_KEY] = images
        dependencies[image.DEP_VERSIONS_KEY] = versions
        return dependencies