docs: def one(self):
          ''' Execute the query and return one result.  If more than one result
              is returned, raises a ``BadResultException``
          '''
          count = -1
          for count, result in enumerate(self):
              if count > 0:
                  raise BadResultException('Too many results for .one()')
          if count == -1:
              raise BadResultException('Too few results for .one()')
          return result