def replace(self, key, value):
super(MergingDict, self).__setitem__(key, value)<EOL>
Convenience method provided as a way to replace a value mapped by a
key.This is required since a MergingDict always merges via assignment
of item/attribute.

:param key: Attribute name or item key to replace rvalue for.
:type key: object
:param value: The new value to assign.
:type value: object
:return: