How to remove border from buttons in google apps script?

In my User Interface for the Google Calendar add-on, I’m attempting to remove the border from my buttons.

While I can create a border style, I’m unable to apply it to my buttons, as newTextButton or newButtonSet does not support borders, resulting in an error.

How can I eliminate the borders from my buttons?

image with border button

// this is my border style varible for removing borders
const bor = CardService.newBorderStyle();
bor.setType(CardService.BorderType.NO_BORDER);

this is my button code

const back_button = CardService.newTextButton()
.setText("CHANGE_HOST_ID")
.setDisabled(false)
.setTextButtonStyle(CardService.TextButtonStyle.TEXT)
.setOnClickAction(back_action_fun);

var buttonSet = CardService.newButtonSet()
.addButton(back_button);

// button then added as a widget

const section = CardService.newCardSection().addWidget(buttonSet);

const card = CardService.newCardBuilder().addSection(section);
return card.build();

I tried these things but none of them worked?

// tried each of them individually 
const back_button = CardService.newBorderStyle(bor).newTextButton().setText("CHANGE_HOST_ID")

const back_button = CardService.newBorderStyle().setType(CardService.BorderType.NO_BORDER).newTextButton().setText("CHANGE_HOST_ID")

const section = CardService.newCardSection().addWidget(buttonSet).newBorderStyle(bor);

const card = CardService.newCardBuilder().newBorderStyle(bor).addSection(section);```