How to use the mson/lib/fields.ButtonField function in mson

block: false
        }),
        new TextField({ name: 'lastName', label: 'Last Name', required: true }),
        new EmailField({ name: 'email', label: 'Email' }),
        new ButtonField({
          name: 'import',
          label: 'Import',
          icon: 'ImportContacts'
        }),
        new ButtonField({
          name: 'submit',
          label: 'Submit',
          type: 'submit',
          icon: 'Save'
        }),
        new ButtonField({ name: 'cancel', label: 'Cancel', icon: 'Cancel' })
      ]
    });

    this.on('import', () => {
      this.setValues({
        firstName: 'Prince',
        lastName: 'Nelson',
        email: 'prince@example.com'
      });
    });

    this.on('submit', () => {
      // TODO: do something like contact an API

      const values = this.getValues();
      console.log('submitting', values);