code: def __call__(self, trainer):
      if self.is_master:
          self.snapshot(trainer)
  
file_path: chainer/chainermn/extensions/_multi_node_snapshot.py
imports: import io
  from chainer.serializers import load_npz
  from chainer.serializers import save_npz
  from chainer.training.extension import Extension
  from chainer.training.extensions._snapshot import _find_latest_snapshot
label_desc: Use image node_id 5 for calling the _MultiNodeSnapshot obj's underlying member method code with example usage: obj.__call__(trainer) without return types