docs: function(className, params, callback) {
          /**
           * Callback for QB.data.deleteFile(className, params, callback)
           * @callback deleteFileFromDataCallback
           * @param {object} error - The error object
           * @param {object} response - Empty body
           */
          this.service.ajax({url: Utils.getUrl(config.urls.data, className + '/' + params.id + '/file'), data: {field_name: params.field_name},
              dataType: 'text', type: 'DELETE'}, function(err, result) {
              if (err) {
                  callback(err, null);
              } else {
                  callback (err, true);
              }
          });
      }