code: def list_backbone_names():
      all_keys = []
      for backbone_type in BACKBONE_REGISTRY.list_keys():
          all_keys.extend(BACKBONE_REGISTRY.get(backbone_type)[-1]())
      return all_keys
  
imports: from typing import Tuple, List
  from ..base import get_model_zoo_home_dir
  from ..data.tokenizers import BaseTokenizer
  from ..utils.registry import Registry
  from mxnet.gluon import Block
label_desc: Use image node_id 1 for calling a global function with example usage: list_backbone_names() and returns: all_keys