How do I downcast in python

How do I downcast in python

References

Reference NO 1

http://stackoverflow.com/questions/15187653/how-do-i-downcast-in-python

Reference NO 2

http://www.gossamer-threads.com/lists/python/python/871571

Reference NO 3

https://groups.google.com/d/topic/comp.lang.python/zdLIM3SHlUM

Reference NO 4

http://jeffelmore.org/tag/django-python-inheritance-downcasting-orm-polymorphism-queryset/

Reference NO 5

http://python.6.x6.nabble.com/Down-casting-Python-objects-td934416.html

Reference NO 6

http://boost.2283326.n4.nabble.com/C-sig-problems-downcasting-from-C-base-class-intrusive-pointers-to-Python-derived-instances-td2699460.html

Reference NO 7

http://code.activestate.com/lists/python-list/311043/

Reference NO 8

http://bytes.com/topic/python/answers/586989-type-casting-base-class-derived-one