code: function (importData, importOptions) {
          importOptions = importOptions || {};
          var ops = [];
          _.each(this.importers, function (importer) {
              if (importData.hasOwnProperty(importer.type)) {
                  ops.push(function () {
                      return importer.doImport(importData[importer.type], importOptions);
                  });
              }
          });
  
          return sequence(ops).then(function (importResult) {
              return importResult;
          });
      }
docs: Import Step 3:
  Each importer gets passed the data from importData which has the key matching its type - i.e. it only gets the
  data that it should import. Each importer then handles actually importing that data into Ghost
  @param {ImportData} importData
  @param {importOptions} importOptions to allow override of certain import features such as locking a user
  @returns {Promise(ImportData)}