code: function(options) {
    if (typeof options !== 'object') {
      throw new ArgumentError('Missing tokens manager options');
    }
  
    if (typeof options.baseUrl !== 'string') {
      throw new ArgumentError('baseUrl field is required');
    }
  
    this.baseUrl = options.baseUrl;
    this.headers = options.headers || {};
    this.clientId = options.clientId || '';
  }
docs: @class
  Provides methods for getting token data and exchanging tokens.
  @constructor
  @memberOf module:auth
  
  @param  {Object}   options               Manager options.
  @param  {String}   options.baseUrl       The auth0 account URL.
  @param  {String}   [options.headers]     Default request headers.
  @param  {String}   [options.clientId]    Default client ID.