Internal Program Version: webencodings  0.5.1

In order to be compatible with legacy web content when interpreting
something like Content-Type: text/html; charset=latin1, tools need
to use a particular set of aliases for encoding labels as well as
some overriding rules. For example, US-ASCII and iso-8859-1 on the
web are actually aliases for windows-1252, and an UTF-8 or UTF-16 BOM
takes precedence over any other encoding declaration. The Encoding
standard defines all such details so that implementations do not have
to reverse-engineer each other.

This module has encoding labels and BOM detection, but the actual
implementation for encoders and decoders is Python’s.

https://pypi.python.org/pypi/webencodings