docstr: get a node by index
docstr_tok: ["get","a","node","by","index"]
code: def get_node_by_idx(self, idx: int) -> Node:
      """
      get a node by index
      """
      return self._node_list[idx]
  
imports: from typing import Any, Dict, List, Union
  from torch.fx.node import Node
  from colossalai.logging import get_dist_logger
label_desc: Use image node_id 5 for calling the NodeMgr obj's underlying member method code with example usage: obj.get_node_by_idx(idx) and returns: self