Return a copy of the object only containing the
        whitelisted properties.

def pick(self, *args):
        """
        Return a copy of the object only containing the
        whitelisted properties.
        """
        ns = self.Namespace()
        ns.result = {}

        def by(key, *args):
            if key in self.obj:
                ns.result[key] = self.obj[key]

        _.each(self._flatten(args, True, []), by)
        return self._wrap(ns.result)