This is a catch all for the multiple requests to update the type definition. Needs to be done for the next release.

test/specs/instance.spec.js
expect(typeof instance.defaults.headers, 'object');
    expect(typeof instance.defaults.headers.common, 'object');
  });
  it('should have interceptors on the instance', function (done) {
    axios.interceptors.request.use(function (config) {
      config.foo = true;
      return config;
    });
    var instance = axios.create();
    instance.interceptors.request.use(function (config) {
      config.bar = true;
      return config;
    });
    var response;
    instance.get('/foo').then(function (res) {
      response = res;
    });
    getAjaxRequest().then(function (request) {
      request.respondWith({
        status: 200
      });
      setTimeout(function () {
        expect(response.config.foo).toEqual(undefined);
        expect(response.config.bar).toEqual(true);
        done();
      });
    });
  });
});