kivy listitem button with checkbox position

I would like to have a list item button with at the right a checkbox. At the moment I have the checkbox in the center and the list item button text also in the center, so both widgets are mixed

How can I shift the checkbox at the right side ?

My class code :

class AttendanceListButton(FloatLayout, ListItemButton, CheckBox):
    root = FloatLayout()
    b1 = ListItemButton(pos_hint={'left': 1, 'center_y': .5}, size_hint=(None, None))
    b2 = CheckBox(pos_hint={'right': 1 , 'center_y': .5}, size_hint=(None, None))
    root.add_widget(b1)
    root.add_widget(b2)

Thank you in advance!