code: function (deviceIdentifier, identifierUrn, data) {
        var path;
        if (deviceIdentifier) {
          path = this.constructPath(constants.DEVICES, deviceIdentifier, constants.IDENTIFIERS, identifierUrn);
          return this.Core.PATCH(path, data);
        } else {
          return this.rejectRequest('Bad Request: A device identifier, an identifier id and a data object are required.');
        }
      }
docs: Add an identifier for a device
  @param  {String|Integer} deviceIdentifier A Robin device identifier
  @param  {String|Integer} identifierUrn    A Robin identifier URN
  @param  {Object}         data             A querystring object
  @return {Function}                        A Promise