Accerciser example rule

check_focusable.py

class CheckFocusable(Validator):
  def condition(self, acc):
    # only test accessibles that have the action interface
    return acc.queryAction()
  def after(self, acc, state, view):
    # check an accessible after checking its descendants
    # acc is the accessible
    # state is a dictionary of whatever you need to store across tests
    # view logs errors, warnings, etc.
    pass
  def before(self, acc, state, view):
    # check an accessible before checking its descendants
    s = acc.getState()
    if not s.contains(STATE_FOCUSABLE):
      view.error('actionable widget is not focusable')