code: function Client(app) {
    if (!(this instanceof Client)) return new Client(app);
    this._base = '';
    this._url = '';
    this.serialize = serializers.raw;
    this.parse = parsers.raw;
    this.middlewares = [];
    this.expectations = [];
    this.options = {
      followRedirect: false,
      method: 'GET',
      headers: {}
    };
  
    if (app) this.app(app);
  }
docs: Client.
  
  @param {Object|Function} HTTP app or HTTP handler
  @constructor