code: def __call__(cls, *args, **kwargs):
      if cls not in cls._instances:
          cls._instances[cls] = super(Singleton, cls).__call__(
              *args, **kwargs
          )
      return cls._instances[cls]
  
imports: import sys
  from typing import Any, Union, Optional
  from rich.progress import Progress, Console, GetTimeCallable, get_console, TaskID, Live, Text, ProgressSample
  from rich.progress import ProgressColumn, TimeRemainingColumn, BarColumn, TimeElapsedColumn, TextColumn
  from fastNLP.envs import get_global_rank
  from .utils import is_notebook
label_desc: Use image node_id 1 for calling the Singleton obj's underlying member method code with example usage: obj.__call__(cls) and returns: cls