How to use the vpython.button function in vpython

def __setup_ui_controls(self, list_of_names):
        """
        The initial configuration of the user interface

        :param list_of_names: A list of names of the robots in the screen
        :type list_of_names: `list`
        """
        # Button to reset camera
        self.scene.append_to_caption('\n')
        btn_reset = button(bind=self.__reset_camera, text="Reset Camera")
        self.scene.append_to_caption('\t')

        chkbox_cam = checkbox(bind=self.__camera_lock_checkbox, text="Camera Lock", checked=self.__camera_lock)
        # Prevent the space bar from toggling the active checkbox/button/etc (default browser behaviour)
        self.scene.append_to_caption('''
            ''')
        # https://stackoverflow.com/questions/22280139/prevent-space-button-from-triggering-any-other-button-click-in-jquery
        self.scene.append_to_caption('\t')

        chkbox_rel = checkbox(bind=self.__grid_relative_checkbox, text="Grid Relative", checked=self.__grid_relative)

event.preventDefault();
                    }
                });
            ''')
        # https://stackoverflow.com/questions/22280139/prevent-space-button-from-triggering-any-other-button-click-in-jquery
        self.scene.append_to_caption('\t')

        chkbox_rel = checkbox(bind=self.__grid_relative_checkbox, text="Grid Relative", checked=self.__grid_relative)
        self.scene.append_to_caption('\n')

        # Drop down for robots / joints in frame
        menu_robots = menu(bind=self.__menu_item_chosen, choices=list_of_names)
        self.scene.append_to_caption('\t')

        # Button to delete the selected robot
        btn_del = button(bind=self.__del_robot, text="Delete Robot")
        self.scene.append_to_caption('\t')

        # Button to clear the robots in screen
        btn_clr = button(bind=self.clear_scene, text="Clear Scene")
        self.scene.append_to_caption('\n')

        # Checkbox for grid visibility
        chkbox_grid = checkbox(bind=self.__grid_visibility_checkbox, text="Grid Visibility", checked=self.__grid_visibility)
        self.scene.append_to_caption('\t')

        # Checkbox for reference frame visibilities
        if len(self.__robots) == 0:
            chkbox_ref = checkbox(bind=self.__reference_frame_checkbox, text="Show Reference Frames", checked=True)
        else:
            chk = self.__robots[self.__selected_robot].ref_shown
            chkbox_ref = checkbox(bind=self.__reference_frame_checkbox, text="Show Reference Frames", checked=chk)

# https://stackoverflow.com/questions/22280139/prevent-space-button-from-triggering-any-other-button-click-in-jquery
        self.scene.append_to_caption('\t')

        chkbox_rel = checkbox(bind=self.__grid_relative_checkbox, text="Grid Relative", checked=self.__grid_relative)
        self.scene.append_to_caption('\n')

        # Drop down for robots / joints in frame
        menu_robots = menu(bind=self.__menu_item_chosen, choices=list_of_names)
        self.scene.append_to_caption('\t')

        # Button to delete the selected robot
        btn_del = button(bind=self.__del_robot, text="Delete Robot")
        self.scene.append_to_caption('\t')

        # Button to clear the robots in screen
        btn_clr = button(bind=self.clear_scene, text="Clear Scene")
        self.scene.append_to_caption('\n')

        # Checkbox for grid visibility
        chkbox_grid = checkbox(bind=self.__grid_visibility_checkbox, text="Grid Visibility", checked=self.__grid_visibility)
        self.scene.append_to_caption('\t')

        # Checkbox for reference frame visibilities
        if len(self.__robots) == 0:
            chkbox_ref = checkbox(bind=self.__reference_frame_checkbox, text="Show Reference Frames", checked=True)
        else:
            chk = self.__robots[self.__selected_robot].ref_shown
            chkbox_ref = checkbox(bind=self.__reference_frame_checkbox, text="Show Reference Frames", checked=chk)
        self.scene.append_to_caption('\t')

        # Checkbox for robot visibility
        if len(self.__robots) == 0: