code: def _main():
      """Run the render_fn with the current flow_state."""
      app_state = AppState(plugin=StreamLitStatePlugin())
  
      # Fetch the information of which flow attaches to this streamlit instance
      flow_state = _reduce_to_flow_scope(
          app_state, flow=os.environ["LIGHTNING_FLOW_NAME"]
      )
  
      # Call the provided render function.
      # Pass it the state, scoped to the current flow.
      render_fn = _get_render_fn_from_environment()
      render_fn(flow_state)
  
file_path: pytorch-lightning/src/lightning/app/frontend/streamlit_base.py
imports: import os
  import pydoc
  from typing import Callable
  from lightning.app.frontend.utils import _reduce_to_flow_scope
  from lightning.app.utilities.app_helpers import StreamLitStatePlugin
  from lightning.app.utilities.state import AppState
label_desc: Use image node_id 2 for calling a global function with example usage: _main() without return types