code: function(userId, playlistId, followerIds, callback) {
      return WebApiRequest.builder(this.getAccessToken())
        .withPath(
          '/v1/users/' +
            encodeURIComponent(userId) +
            '/playlists/' +
            playlistId +
            '/followers/contains'
        )
        .withQueryParameters({
          ids: followerIds.join(',')
        })
        .build()
        .execute(HttpManager.get, callback);
    }
docs: Check if users are following a playlist.
  @param {string} userId The playlist's owner's user ID
  @param {string} playlistId The playlist's ID
  @param {String[]} User IDs of the following users
  @param {requestCallback} [callback] Optional callback method to be called instead of the promise.
  @returns {Promise|undefined} A promise that if successful returns an array of booleans. If rejected,
  it contains an error object. Not returned if a callback is given.