sendButtonTemplate(recipientId, text, buttons, options) {
    const payload = {
      template_type: 'button',
      text
    };
    const formattedButtons = this._formatButtons(buttons);
    payload.buttons = formattedButtons;
    return this.sendTemplate(recipientId, payload, options);
  }
@param {Recipient|String} recipientId
@param {String} text Message to be sent.
@param {Array.<String|Button>} buttons
@param {SendMessageOptions} [options]