code: function (identifier, params) {
      var path = this.constructPath(constants.DEVICES, identifier);
      return this.Core.GET(path, params);
    }
docs: Get all the devices or a particular device identified by the `identifier` parameter
  @param  {String|Integer|undefined} identifier A Robin device identifier
  @param  {Object|undefined}         params     A querystring object
  @return {Function}                            A Promise