code: function isHelperGroup(helpers) {
    if (!helpers) return false;
    if (helpers.isGroup) {
      return true;
    }
    if (typeof helpers === 'function' || isObject(helpers)) {
      var keys = Object.keys(helpers).filter(function(name) {
        return ['async', 'sync', 'displayName'].indexOf(name) === -1;
      });
      return keys.length > 1;
    }
    return false;
  }
docs: Return true if the given value is a helper "group"