How to use the cekit.tools.load_descriptor function in cekit

def init(self):
        """
        Initializes the image object.
        """

        LOGGER.debug("Removing old target directory")
        shutil.rmtree(self.target, ignore_errors=True)
        os.makedirs(os.path.join(self.target, 'image'))

        # Read the main image descriptor and create an Image object from it
        descriptor = tools.load_descriptor(self._descriptor_path)

        if isinstance(descriptor, list):
            LOGGER.info("Descriptor contains multiple elements, assuming multi-stage image")
            LOGGER.info("Found {} builder image(s) and one target image".format(
                len(descriptor[:-1])))

            # Iterate over images defined in image descriptor and
            # create Image objects out of them
            for image_descriptor in descriptor[:-1]:
                self.builder_images.append(
                    Image(image_descriptor, os.path.dirname(os.path.abspath(self._descriptor_path))))

            descriptor = descriptor[-1]

        self.image = Image(descriptor, os.path.dirname(os.path.abspath(self._descriptor_path)))

def load_repository(self, repo_dir):
        for modules_dir, _, files in os.walk(repo_dir):
            if 'module.yaml' in files:

                module_descriptor_path = os.path.abspath(os.path.expanduser(
                    os.path.normcase(os.path.join(modules_dir, 'module.yaml'))))

                module = Module(tools.load_descriptor(module_descriptor_path),
                                modules_dir,
                                os.path.dirname(module_descriptor_path))
                logger.debug("Adding module '%s', path: '%s'" % (module.name, module.path))
                self._module_registry.add_module(module)