How to use the labelme.label_file.LabelFile function in labelme

def is_label_file(filename):
        return osp.splitext(filename)[1].lower() == LabelFile.suffix

if not QtCore.QFile.exists(filename):
            self.errorMessage(
                self.tr('Error opening file'),
                self.tr('No such file: <b>%s</b>') % filename
            )
            return False
        # assumes same name, but json extension
        self.status(self.tr("Loading %s...") % osp.basename(str(filename)))
        label_file = osp.splitext(filename)[0] + '.json'
        if self.output_dir:
            label_file_without_path = osp.basename(label_file)
            label_file = osp.join(self.output_dir, label_file_without_path)
        if QtCore.QFile.exists(label_file) and \
                LabelFile.is_label_file(label_file):
            try:
                self.labelFile = LabelFile(label_file)
            except LabelFileError as e:
                self.errorMessage(
                    self.tr('Error opening file'),
                    self.tr(
                        "<p><b>%s</b></p>"
                        "<p>Make sure <i>%s</i> is a valid label file."
                    ) % (e, label_file)
                )
                self.status(self.tr("Error reading %s") % label_file)
                return False
            self.imageData = self.labelFile.imageData
            self.imagePath = osp.join(
                osp.dirname(label_file),
                self.labelFile.imagePath,
            )
            if self.labelFile.lineColor is not None:</p>

if self.output_dir:
            dlg = QtWidgets.QFileDialog(
                self, caption, self.output_dir, filters
            )
        else:
            dlg = QtWidgets.QFileDialog(
                self, caption, self.currentPath(), filters
            )
        dlg.setDefaultSuffix(LabelFile.suffix[1:])
        dlg.setAcceptMode(QtWidgets.QFileDialog.AcceptSave)
        dlg.setOption(QtWidgets.QFileDialog.DontConfirmOverwrite, False)
        dlg.setOption(QtWidgets.QFileDialog.DontUseNativeDialog, False)
        basename = osp.basename(osp.splitext(self.filename)[0])
        if self.output_dir:
            default_labelfile_name = osp.join(
                self.output_dir, basename + LabelFile.suffix
            )
        else:
            default_labelfile_name = osp.join(
                self.currentPath(), basename + LabelFile.suffix
            )
        filename = dlg.getSaveFileName(
            self, self.tr('Choose File'), default_labelfile_name,
            self.tr('Label files (*%s)') % LabelFile.suffix)
        if QT5:
            filename, _ = filename
        filename = str(filename)
        return filename

dlg.setDefaultSuffix(LabelFile.suffix[1:])
        dlg.setAcceptMode(QtWidgets.QFileDialog.AcceptSave)
        dlg.setOption(QtWidgets.QFileDialog.DontConfirmOverwrite, False)
        dlg.setOption(QtWidgets.QFileDialog.DontUseNativeDialog, False)
        basename = osp.basename(osp.splitext(self.filename)[0])
        if self.output_dir:
            default_labelfile_name = osp.join(
                self.output_dir, basename + LabelFile.suffix
            )
        else:
            default_labelfile_name = osp.join(
                self.currentPath(), basename + LabelFile.suffix
            )
        filename = dlg.getSaveFileName(
            self, self.tr('Choose File'), default_labelfile_name,
            self.tr('Label files (*%s)') % LabelFile.suffix)
        if QT5:
            filename, _ = filename
        filename = str(filename)
        return filename