There is a duplication of the first section of 18.2.2 (JSON) Encoders and Decoders of the python 2.7.9RC1 doc as well of the corresponding paragraph in 19.2.2 of the Python 3 docs.
The section documents JSONDecoder and then JSONEncoder. Looking at the current 3.4 online docs, I do not see any significant duplication within either entry. Even if there were duplication between, we might leave it to keep the entries complete in themselves. But not seeing any, this is moot.