def _sort_resources_per_hosting_device(resources):
        """This function will sort the resources on hosting device.

        The sorting on hosting device is done by looking up the
        `hosting_device` attribute of the resource, and its `id`.

        :param resources: a dict with key of resource name
        :return dict sorted on the hosting device of input resource. Format:
        hosting_devices = {
                            'hd_id1' : {'routers':[routers],
                                        'removed_routers':[routers], .... }
                            'hd_id2' : {'routers':[routers], .. }
                            .......
                            }
        """
        hosting_devices = {}
        for key in resources.keys():
            for r in resources.get(key) or []:
                if r.get('hosting_device') is None:
                    continue
                hd_id = r['hosting_device']['id']
                hosting_devices.setdefault(hd_id, {})
                hosting_devices[hd_id].setdefault(key, []).append(r)
        return hosting_devices
This function will sort the resources on hosting device.

        The sorting on hosting device is done by looking up the
        `hosting_device` attribute of the resource, and its `id`.

        :param resources: a dict with key of resource name
        :return dict sorted on the hosting device of input resource. Format:
        hosting_devices = {
                            'hd_id1' : {'routers':[routers],
                                        'removed_routers':[routers], .... }
                            'hd_id2' : {'routers':[routers], .. }
                            .......
                            }