code: def migrateDown(self):
          
          ss = self.avatars.open()
          def _():
              oldAccounts = ss.query(LoginAccount)
              oldMethods = ss.query(LoginMethod)
              for x in list(oldAccounts) + list(oldMethods):
                  x.deleteFromStore()
              self.cloneInto(ss, ss)
              IScheduler(ss).migrateDown()
          ss.transact(_)
docs: Assuming that self.avatars is a SubStore which should contain *only*
          the LoginAccount for the user I represent, remove all LoginAccounts and
          LoginMethods from that store and copy all methods from the site store
          down into it.