def test_from_namespaces(self):
     """Test construction from list of namespaces."""
     self.assertEqual(RegexSet.from_namespaces([]), RegexSet([], []))
     self.assertEqual(
         RegexSet.from_namespaces(["db.bar", "db_*.foo", "db2.*"]),
         RegexSet(
             [namespace_to_regex("db_*.foo"),
              namespace_to_regex("db2.*")], ["db.bar"]))