class_docstr: CheckpointManager is a class abstraction to manage a training job's
  checkpoints/snapshots with different IO and storage.
docstr: Return all existing checkpoint paths
  Returns: checkpoint_path_list (List[str]), list elements are in the same
  order of checkpoint saving
docstr_tok: ["Return","all","existing","checkpoint","paths","Returns",":","checkpoint_path_list","(","List","[","str","]",")",",","list","elements","are","in","the","same","order","of","checkpoint","saving"]
code: def list(self) -> List[str]:
      """
      Return all existing checkpoint paths
      Returns: checkpoint_path_list (List[str]), list elements are in the same
      order of checkpoint saving
      """
      raise NotImplementedError("Not implemented in interface class")
  
imports: import abc
  from typing import List
  import torch
  from pytext.utils.file_io import PathManager
  from pytext.utils.usage import log_class_usage
label_desc: Use image node_id 4 for calling the PyTextCheckpointManagerInterface obj's underlying member method code with example usage: obj.list() without return types