code: function (streamInfo) {
      if (!streamInfo) {
        return this.get('_revision');
      }
      streamInfo.context = streamInfo.context || '_general';
      return this.get('_revisions')[streamInfo.context + '_' + streamInfo.aggregate + '_' + streamInfo.aggregateId] || 0;
    }
docs: Returns the revision of this aggregate.
  @param {Object} streamInfo The stream info.
  @returns {Number}