I am trying to use a customClass for the buttons like this:

this.$dialog
        .confirm('Are you sure you want to delete the selected users.', {
          okText: 'Delete',
          cancelText: 'Cancel',
          customClass: {
            cancel: 'btn btn-light btn-sm'
          }
        })
        .then(function(dialog) {
          this.deleteSelectedUsers()
        })

However I do not see the classes mentioned above applied to the cancel button. I am using bootstrap and these classes are part of it. I can manually change the class of cancel button through inspector and see the desired result , but the above code is not resulting in the above classes applied.