code: function (deviceIdentifier, channelIdentifier, params) {
        var path;
        if (deviceIdentifier) {
          path = this.constructPath(constants.DEVICES, deviceIdentifier, constants.CHANNELS, channelIdentifier);
          return this.Core.GET(path, params);
        } else {
          return this.rejectRequest('Bad Request: A device identifier is required.');
        }
      }
docs: Get all the channels for a device or a particular channel identified by `channelIdentifier`
  @param  {String|Integer}           deviceIdentifier  A Robin device identifier
  @param  {String|Integer|undefined} channelIdentifier A Robin channel identifier
  @param  {Object|undefined}         params            A querystring object
  @return {Function}                                   A Promise