'Return (filled frame, options) for testing.
Options is a list of searchengine booleanvar, label pairs.
A gridded frame from make_frame is filled with a Checkbutton
for each pair, bound to the var, with the corresponding label.'

def create_option_buttons(self):

    frame = self.make_frame('Options')[0]
    engine = self.engine
    options = [(engine.revar, 'Regular    expression'), (engine.casevar, 'Match    case'), (engine.wordvar, 'Whole    word')]
    if self.needwrapbutton:
        options.append((engine.wrapvar, 'Wrap    around'))
    for (var, label) in options:
        btn = Checkbutton(frame, variable=var, text=label)
        btn.pack(side='left', fill='both')
    return (frame, options)
