def get_debug_flag() -> bool:
    """Get whether debug mode should be enabled for the app, indicated by the
    :envvar:`FLASK_DEBUG` environment variable. The default is ``False``.
    """
    val = os.environ.get("FLASK_DEBUG")
    return bool(val and val.lower() not in {"0", "false", "no"})
Get whether debug mode should be enabled for the app, indicated by the
    :envvar:`FLASK_DEBUG` environment variable. The default is ``False``.
    
src/flask/helpers.py