code: def getInstruments(self):
          
          query = {"portal_type": "Instrument", "is_active": True}
  
          if self.getRestrictToMethod():
              query.update({
                  "getMethodUIDs": {
                      "query": api.get_uid(self.getRestrictToMethod()),
                      "operator": "or",
                  }
              })
  
          instruments = api.search(query, "bika_setup_catalog")
          items = map(lambda i: (i.UID, i.Title), instruments)
  
          instrument = self.getInstrument()
          if instrument:
              instrument_uids = map(api.get_uid, instruments)
              if api.get_uid(instrument) not in instrument_uids:
                  items.append(
                      (api.get_uid(instrument), api.get_title(instrument)))
  
          items.sort(lambda x, y: cmp(x[1], y[1]))
          items.insert(0, ("", _("No instrument")))
  
          return DisplayList(list(items))
docs: Get the allowed instruments