How to use the @jupyterlab/docmanager.getOpenPath function in @jupyterlab/docmanager

execute: () => {
      return getOpenPath(docManager.services.contents).then(path => {
        if (!path) {
          return;
        }
        docManager.services.contents.get(path, { content: false }).then(
          args => {
            // exists
            return commands.execute(CommandIDs.open, { path: path });
          },
          () => {
            // does not exist
            return showDialog({
              title: 'Cannot open',
              body: 'File not found',
              buttons: [Dialog.okButton()]
            });
          }