Get handle for image group resource at given Url.

        Parameters
        ----------
        resource_url : string
            Url for image group resource at SCO-API

        Returns
        -------
        scoserv.ImageGroupHandle
            Handle for local copy of image group resource

def image_groups_get(self, resource_url):
        """Get handle for image group resource at given Url.

        Parameters
        ----------
        resource_url : string
            Url for image group resource at SCO-API

        Returns
        -------
        scoserv.ImageGroupHandle
            Handle for local copy of image group resource
        """
        # Get resource directory, Json representation, active flag, and cache id
        obj_dir, obj_json, is_active, cache_id = self.get_object(resource_url)
        # Create image group handle. Will raise an exception if resource is not
        # in cache and cannot be downloaded.
        image_group = ImageGroupHandle(obj_json, obj_dir)
        # Add resource to cache if not exists
        if not cache_id in self.cache:
            self.cache_add(resource_url, cache_id)
        # Return image group handle
        return image_group