Click (and choose) the radio button with the given label (recommended),
    name or id.

def choose_radio(self, value):
    """
    Click (and choose) the radio button with the given label (recommended),
    name or id.
    """
    box = find_field(world.browser, 'radio', value)
    assert box, "Cannot find a '{}' radio button.".format(value)
    box.click()