def __repr__(self):
        return "<NamedRequirements({}{})>".format(
            self.name,
            ", filename='{}'".format(self.filename.name) if self.filename
            else "")
def get_bind(self, mapper=None, *args, **kwargs):
                    return super(MySession, self).get_bind(
                        mapper, *args, **kwargs
                    )