How to use the iview/src/components/message.error function in iview

error(config) {
    if (typeof config === 'string')
      return message.error({
        content: config,
        duration: 5,
      })
    if (typeof config === 'object')
      return message.error({
        duration: 5,
        ...config,
      })
  },
  loading(config) {

.catch(err => {
                    Message.error(err.body.error);
                });
        },

.catch(err => {
                    this.loading = false;
                    this.message = err.body.error;
                    if (err.status !== 401) {
                        Message.error(err.body.error);
                        return;
                    }
                    if (err.body.passwordRequired) {
                        this.auth.passwordRequired = true;
                    } else {
                        this.auth.private = true;
                    }
                });
        },

.catch(err => {
                        Message.error(err.body.error);
                    });
            } else {

.catch(res => {
                        Message.error(res.body.error);
                    });
            } else {