code: def flush(self, key=None):
      if key is None:
          for k, f in self.handles.items():
              self._write_buffer(k)
              f.flush()
      elif isinstance(key, list):
          for k in key:
              self._write_buffer(k)
              self.handles[k].flush()
      else:
          self._write_buffer(key)
          self.handles[key].flush()
  
imports: import os
  import time
  import torch
  import traceback
  from contextlib import contextmanager
  import jiant.utils.python.io
  import jiant.utils.python.filesystem
label_desc: Use image node_id 5 for calling the ZBufferedLogger obj's underlying member method code with example usage: obj.flush(key) without return types