code: def _sequenceContainer(self, store):
          
          if self._sequence is None:
              self._sequence = list(self.container)
              self._clause = ', '.join(['?'] * len(self._sequence))
          return self._clause
docs: Smash whatever we got into a list and save the result in case we are
          executed multiple times.  This keeps us from tripping up over
          generators and the like.