code: def locked_get(self):
          
          filters = {self.key_name: self.key_value}
          query = self.session.query(self.model_class).filter_by(**filters)
          entity = query.first()
  
          if entity:
              credential = getattr(entity, self.property_name)
              if credential and hasattr(credential, 'set_store'):
                  credential.set_store(self)
              return credential
          else:
              return None
docs: Retrieve stored credential.
  
          Returns:
              A :class:`oauth2client.Credentials` instance or `None`.