code: function(playlistId, callback) {
      return WebApiRequest.builder(this.getAccessToken())
        .withPath('/v1/playlists/' + playlistId + '/followers')
        .withHeaders({ 'Content-Type': 'application/json' })
        .build()
        .execute(HttpManager.del, callback);
    }
docs: Unfollow a playlist.
  @param {string} playlistId The playlist's ID
  @param {Object} [options] The possible options, currently only public.
  @param {requestCallback} [callback] Optional callback method to be called instead of the promise.
  @returns {Promise|undefined} A promise that if successful, simply resolves to an empty object. If rejected,
  it contains an error object. Not returned if a callback is given.