code: function(userIds, callback) {
      return WebApiRequest.builder(this.getAccessToken())
        .withPath('/v1/me/following')
        .withQueryParameters({
          ids: userIds.join(','),
          type: 'user'
        })
        .build()
        .execute(HttpManager.del, callback);
    }
docs: Remove the current user as a follower of one or more other Spotify users.
  @param {string[]} userIds The IDs of the users to be unfollowed.
  @param {requestCallback} [callback] Optional callback method to be called instead of the promise.
  @example unfollowUsers(['thelinmichael', 'wizzler']).then(...)
  @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.