code: function getInstancesOf(_typeName) {
          var _instances = [],
              _typeNames = [];
  
          if (_.isArray(_typeName)) {
              _typeNames = _typeName;
          } else if (_.isString(_typeName)) {
              _typeNames.push(_typeName);
          }
  
          _.each(_idMap, function (elem) {
              var i, len, _typeTest = false;
  
              for (i = 0, len = _typeNames.length; i < len; i++) {
                  if (elem instanceof _global.type[_typeNames[i]]) {
                      _typeTest = true;
                      break;
                  }
              }
  
              if (_typeTest) {
                  _instances.push(elem);
              }
          });
  
          return _instances;
      }
docs: Return instances of a specified type name(s).
  @param {string|Array.<string>} _typeName Type name(s) of instances to be returned.
  @return {Array.<Element>} instances of the type name(s).