code: def _index(self, item):
          '''Return index of *item* in member list or -1 if not present.'''
          index = bisect.bisect_left(self._members, item)
          if index != len(self) and self._members[index] == item:
              return index
  
          return -f _index(self, item):
          '''Return index of *item* in member list or -1 if not present.'''
          index = bisect.bisect_left(self._members, item)
          if index != len(self) and self._members[index] == item:
              return index
  
          return -1
docs: Return index of *item* in member list or -1 if not present.