How to use the labelme.logger.logger.warn function in labelme

def get_default_config():
    config_file = osp.join(here, 'default_config.yaml')
    with open(config_file) as f:
        config = yaml.safe_load(f)

    # save default config to ~/.labelmerc
    user_config_file = osp.join(osp.expanduser('~'), '.labelmerc')
    if not osp.exists(user_config_file):
        try:
            shutil.copy(config_file, user_config_file)
        except Exception:
            logger.warn('Failed to save config: {}'.format(user_config_file))

    return config

self.labelList.itemDoubleClicked.connect(self.labelDoubleClicked)
        self.edit.setListWidget(self.labelList)
        layout.addWidget(self.labelList)
        # label_flags
        if flags is None:
            flags = {}
        self._flags = flags
        self.flagsLayout = QtWidgets.QVBoxLayout()
        self.resetFlags()
        layout.addItem(self.flagsLayout)
        self.edit.textChanged.connect(self.updateFlags)
        self.setLayout(layout)
        # completion
        completer = QtWidgets.QCompleter()
        if not QT5 and completion != 'startswith':
            logger.warn(
                "completion other than 'startswith' is only "
                "supported with Qt5. Using 'startswith'"
            )
            completion = 'startswith'
        if completion == 'startswith':
            completer.setCompletionMode(QtWidgets.QCompleter.InlineCompletion)
            # Default settings.
            # completer.setFilterMode(QtCore.Qt.MatchStartsWith)
        elif completion == 'contains':
            completer.setCompletionMode(QtWidgets.QCompleter.PopupCompletion)
            completer.setFilterMode(QtCore.Qt.MatchContains)
        else:
            raise ValueError('Unsupported completion: {}'.format(completion))
        completer.setModel(self.labelList.model())
        self.edit.setCompleter(completer)

copy,
            delete,
            undo,
            None,
            zoomIn,
            zoom,
            zoomOut,
            fitWindow,
            fitWidth,
        )

        self.statusBar().showMessage(self.tr('%s started.') % __appname__)
        self.statusBar().show()

        if output_file is not None and self._config['auto_save']:
            logger.warn(
                'If `auto_save` argument is True, `output_file` argument '
                'is ignored and output filename is automatically '
                'set as IMAGE_BASENAME.json.'
            )
        self.output_file = output_file
        self.output_dir = output_dir

        # Application state.
        self.image = QtGui.QImage()
        self.imagePath = None
        self.recentFiles = []
        self.maxRecent = 7
        self.lineColor = None
        self.fillColor = None
        self.otherData = None
        self.zoom_level = 100

def update_dict(target_dict, new_dict, validate_item=None):
    for key, value in new_dict.items():
        if validate_item:
            validate_item(key, value)
        if key not in target_dict:
            logger.warn('Skipping unexpected key in config: {}'
                        .format(key))
            continue
        if isinstance(target_dict[key], dict) and \
                isinstance(value, dict):
            update_dict(target_dict[key], value, validate_item=validate_item)
        else:
            target_dict[key] = value

def labelme_shapes_to_label(img_shape, shapes):
    logger.warn('labelme_shapes_to_label is deprecated, so please use '
                'shapes_to_label.')

    label_name_to_value = {'_background_': 0}
    for shape in shapes:
        label_name = shape['label']
        if label_name in label_name_to_value:
            label_value = label_name_to_value[label_name]
        else:
            label_value = len(label_name_to_value)
            label_name_to_value[label_name] = label_value

    lbl = shapes_to_label(img_shape, shapes, label_name_to_value)
    return lbl, label_name_to_value