Use Toggle Buttons as Radio buttons, how to un-toggle other buttons when one is selected

I'm Trying to use toggle buttons as radio buttons and have been unable to get the other buttons to
be de-selected.

There are 3 buttons each has a selected icon and unselected icon.

When I click any of them the selected icon gets displayed and when I click the same button the unselected
icon is displayed, but only for the button clicked. I want to select any button and make the 2 others
unselected.

I've tried
def OnButtonOne(self, event):
      self.buttonTwo.SetSelected(false)
      self.buttonThree.SetSelected(false)

also
def OnButtonOne(self, event):
      self.buttonTwo.SetSelected(false)
      self.buttonTwo.Show()
      self.buttonThree.SetSelected(false)
      self.buttonTwo.Show()

also
def OnButtonOne(self, event):
      self.buttonTwo.SetActive(false)
      self.buttonTwo.Show()
      self.buttonThree.SetActive(false)
      self.buttonTwo.Show()

In another language I remember doing something like
buttonTwo.doClick()
buttonThree.doClick()

But I don't know if Python has something like this

How can I toggle the other two buttons when any one of them is selected?