code: function (fn) {
        return function (exp, msg) {
          /*eslint-disable no-invalid-this*/
          // Set properties.
          this._$el = flag(this, "object");
          this._name = _elName(this._$el);
  
          // Flag message.
          if (msg) {
            flag(this, "message", msg);
          }
  
          // Invoke assertion function.
          fn.apply(this, arguments);
        };
      }
docs: ------------------------------------------------------------------------ Assertions (Internal) ------------------------------------------------------------------------ /*!
  Wrap assert function and add properties.