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