code: function (file, ext) {
          var fileHandler = _.find(this.handlers, function (handler) {
              return _.includes(handler.extensions, ext);
          });
  
          return fileHandler.loadFile([_.pick(file, 'name', 'path')]).then(function (loadedData) {
              // normalize the returned data
              var importData = {};
              importData[fileHandler.type] = loadedData;
              return importData;
          });
      }
docs: Process File
  Takes a reference to a single file, sends it to the relevant handler to be loaded and returns an object in the
  importData format: {data: {}, images: []}
  The data key contains JSON representing any data that should be imported
  The image key contains references to images that will be stored (and where they will be stored)
  @param {File} file
  @returns {Promise(ImportData)}