code: function (meta, fn) {
      if (!_.isObject(meta) || meta.version === undefined || meta.version === null || !_.isNumber(meta.version)) {
        throw new Error('Please pass in a version');
      }
      if (!_.isFunction(fn)) {
        throw new Error('Please pass in a function');
      }
  
      var wrappedFn;
      if (fn.length === 1) {
        wrappedFn = function (s, cb) {
          try {
            cb(null, fn(s));
          } catch (err) {
            cb(err);
          }
        };
      } else {
        wrappedFn = fn;
      }
  
      this.loadingSnapshotTransformerRegistrations.push({ meta: meta, fn: wrappedFn });
      return this;
    }
docs: Defines a new loading transform function for snapshot.
  @param {Object}   meta Meta infos like: { version: 10 }
  @param {Function} fn   Function containing the transform function
  `function(snapshotData, callback){}`
  @returns {Aggregate}