def __repr__(self):
        return "<Requirement(package={package}, version='{version}')>".format(
            package=self.package, version=self.version)
def list_snapshots(self, params=None):
        """List all the snapshot."""
        url = 'snapshots'
        if params:
                url += '?%s' % urllib.urlencode(params)

        resp, body = self.get(url)
        body = json.loads(body)
        return resp, body['snapshots']