code: function Dict_getAsync(key1, key2, key3) {
        var value;
        var xref = this.xref;
        if (typeof (value = this.map[key1]) !== 'undefined' || key1 in this.map ||
            typeof key2 === 'undefined') {
          if (xref) {
            return xref.fetchIfRefAsync(value);
          }
          return Promise.resolve(value);
        }
        if (typeof (value = this.map[key2]) !== 'undefined' || key2 in this.map ||
            typeof key3 === 'undefined') {
          if (xref) {
            return xref.fetchIfRefAsync(value);
          }
          return Promise.resolve(value);
        }
        value = this.map[key3] || null;
        if (xref) {
          return xref.fetchIfRefAsync(value);
        }
        return Promise.resolve(value);
      }
docs: Same as get(), but returns a promise and uses fetchIfRefAsync().