code: function setDefaults(plugin, message, opts) {
    if (typeof plugin === 'object') {
      return defaults(plugin);
    }
    opts = opts || {};
    if (message instanceof Error) {
      opts.error = message;
    } else if (typeof message === 'object') {
      opts = message;
    } else {
      opts.message = message;
    }
    opts.plugin = plugin;
    return defaults(opts);
  }
docs: Set default options based on arguments.