code: def get_test_string(self):
      return f"Hello from {self.__class__.__name__}!"
  
file_path: pytorch-lightning/tests/tests_app/utilities/testdata/safe_pickle_app.py
imports: import subprocess
  from pathlib import Path
  from lightning.app import LightningApp, LightningFlow, LightningWork
  from lightning.app.utilities import safe_pickle
label_desc: Use image node_id 2 for calling the SelfPicklingWork obj's underlying member method code with example usage: obj.get_test_string() and returns: str, self, str