Make classes safe_load/safe_dump compatible.
Make classes safe_load/safe_dump compatible.

This fixes SessionTestCase.test_session_decision_tree.

vishwaprakashmishra/xmatrix,TouK/vumi,harrissoerja/vumi,vishwaprakashmishra/xmatrix,harrissoerja/vumi,harrissoerja/vumi,TouK/vumi,vishwaprakashmishra/xmatrix,TouK/vumi