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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _getInstrumentsVoc(self):
 """ This function returns the registered instruments in the system as a vocabulary. The instruments are filtered by the selected method. """

        cfilter = {'portal_type': 'Instrument', 'is_active': True}
        if self.getMethod():
            cfilter['getMethodUIDs'] = {"query": self.getMethod().UID(),
                                        "operator": "or"}
        bsc = getToolByName(self, 'bika_setup_catalog')
        items = [('', 'No instrument')] + [
            (o.UID, o.Title) for o in
            bsc(cfilter)]
        o = self.getInstrument()
        if o and o.UID() not in [i[0] for i in items]:
            items.append((o.UID(), o.Title()))
        items.sort(lambda x, y: cmp(x[1], y[1]))
        return DisplayList(list(items))