docstr: A context for setting the ScriptRunner._execing flag.
  
  Used by _maybe_handle_execution_control_request to ensure that
  we only handle requests while we're inside an exec() call
docstr_tok: ["A","context","for","setting","the","ScriptRunner._execing","flag",".","Used","by","_maybe_handle_execution_control_request","to","ensure","that","we","only","handle","requests","while","we","'re","inside","an","exec","(",")","call"]
code: def _set_execing_flag(self):
      """A context for setting the ScriptRunner._execing flag.
  
      Used by _maybe_handle_execution_control_request to ensure that
      we only handle requests while we're inside an exec() call
      """
      if self._execing:
          raise RuntimeError("Nested set_execing_flag call")
      self._execing = True
      try:
          yield
      finally:
          self._execing = False
  
imports: import gc
  import sys
  import threading
  import types
  from contextlib import contextmanager
  from enum import Enum
  from timeit import default_timer
  from typing import Callable, Dict, Optional
  from blinker import Signal
  from streamlit import config, runtime, source_util, util
  from streamlit.error_util import handle_uncaught_app_exception
  from streamlit.logger import get_logger
  from streamlit.proto.ClientState_pb2 import ClientState
  from streamlit.proto.ForwardMsg_pb2 import ForwardMsg
  from streamlit.runtime.scriptrunner.script_cache import ScriptCache
  from streamlit.runtime.scriptrunner.script_requests import RerunData, ScriptRequests, ScriptRequestType
  from streamlit.runtime.scriptrunner.script_run_context import ScriptRunContext, add_script_run_ctx, get_script_run_ctx
  from streamlit.runtime.state import SCRIPT_RUN_WITHOUT_ERRORS_KEY, SafeSessionState, SessionState
  from streamlit.runtime.uploaded_file_manager import UploadedFileManager
  from streamlit.vendor.ipython.modified_sys_path import modified_sys_path
label_desc: Use image node_id 12 for calling the ScriptRunner obj's underlying member method code with example usage: obj._set_execing_flag() without return types