def __init__(self, groups=None):
        super(GroupedRequirements, self).__init__(NamedRequirements)
        self.groups = groups or self.default_groups
        self.filename = None
        self.create_default_groups()
def get_bind(self, mapper=None, **kwargs):
                    return super(MySession, self).get_bind(
                        mapper=mapper, **kwargs
                    )