'Write a credentials to the SQLAlchemy datastore.
Args:
credentials: :class:`oauth2client.Credentials`'

def locked_put(self, credentials):

    filters = {self.key_name: self.key_value}
    query = self.session.query(self.model_class).filter_by(**filters)
    entity = query.first()
    if (not entity):
        entity = self.model_class(**filters)
    setattr(entity, self.property_name, credentials)
    self.session.add(entity)
