@staticmethod
def _get_router_ids_from_removed_devices_info(removed_devices_info):
    """Extract router_ids from the removed devices info dict.

        :param removed_devices_info: Dict of removed devices and their
               associated resources.
        Format:
                {
                  'hosting_data': {'hd_id1': {'routers': [id1, id2, ...]},
                                   'hd_id2': {'routers': [id3, id4, ...]},
                                   ...
                                  },
                  'deconfigure': True/False
                }
        :return removed_router_ids: List of removed router ids
        """
    removed_router_ids = []
    for hd_id, resources in removed_devices_info['hosting_data'].items():
        removed_router_ids += resources.get('routers', [])
    return removed_router_ids
