def test_filters_are_clones_not_references(self):
     """_filter must be cloned"""
     # Everything else is considered immutable
     qs = FBO(
         path=TEST_FILES_ROOT,
         glob='*.rst',
     )
     self.assertEqual(
         3,
         qs.count(),
     )
     qs2 = qs.filter(name='test1.rst')
     self.assertEqual(
         3,
         qs.count(),
     )