code: def _merge_states(a: SessionState, b: SessionState) -> None:
      """Merge 'b' into 'a'."""
      a._new_session_state.update(b._new_session_state)
      a._new_widget_state.update(b._new_widget_state)
      a._old_state.update(b._old_state)
      a._key_id_mapping.update(b._key_id_mapping)
  
file_path: streamlit/lib/tests/streamlit/runtime/state/strategies.py
imports: from hypothesis import strategies
  from streamlit.runtime.state.common import GENERATED_WIDGET_ID_PREFIX
  from streamlit.runtime.state.session_state import SessionState, WidgetMetadata
label_desc: Use image node_id 4 for calling a global function with example usage: _merge_states(a, b) without return types