'Replace the current prefs with the new set
@param prefs {list of dict} The new preferences'

def override_prefs(self, prefs):

    changed_prefs = set()
    changed_prefs.update(*(level.keys() for level in self._prefs))
    self._prefs = [level.copy() for level in prefs]
    changed_prefs.update(*(level.keys() for level in self._prefs))
    for pref in changed_prefs:
        self._notify_pref_observers(pref)
