code: function(volumePercent, options, callback) {
      var params = {
        /* jshint camelcase: false */
        volume_percent: volumePercent
      };
      if (options && 'device_id' in options) {
        /* jshint camelcase: false */
        params.device_id = options.device_id;
      }
      return WebApiRequest.builder(this.getAccessToken())
        .withPath('/v1/me/player/volume')
        .withQueryParameters(params)
        .build()
        .execute(HttpManager.put, callback);
    }
docs: Set the volume for the user’s current playback device.
  
  @param {number} volumePercent The volume to set. Must be a value from 0 to 100 inclusive.
  @param {Object} options A JSON object with options that can be passed.
  @param {function(Object,Object)} callback An optional callback that receives 2 parameters. The first
  one is the error object (null if no error), and the second is the value if the request succeeded.
  @return {Object} Null if a callback is provided, a `Promise` object otherwise