code: function (namespace, names){
      if (names){
        for (let i = 0, n = names.length; i < n; ++i){
          let typeName = names[i];
          if (namespace.names.hasOwnProperty(typeName)){
            this.names[typeName] = namespace.names[typeName];
          }
          else {
            throw new ReferenceError('import error: undefined type \'' + typeName + '\'');
          }
        }
      }
      else {
        // import *
        for (let typeName in namespace.names){
          if (namespace.names.hasOwnProperty(typeName)){
            this.names[typeName] = namespace.names[typeName];
          }
        }
      }
      return this;
    }
docs: Import type names from another namespace.
  @param {TemplateNamespace} namespace
  @param {Array<String>} [names] - names to import
  @returns {TemplateNamespace}