from SF patch http://www.python.org/sf/554192
This adds two new functions to mimetypes:
guess_all_extensions() which returns a list of all known
extensions for a mime type, and add_type() which adds one
mapping between a mime type and an extension.
non-standard but common types. Including Martin's suggestion to add
rejected non-standard types from patch #438790. Specifically,
guess_type(), guess_extension(): Both the functions and the methods
grow an optional "strict" flag, defaulting to true, which determines
whether to recognize non-standard, but commonly found types or not.
Also, I sorted, reformatted, and culled duplicates from the big
types_map dictionary. Note that there are a few non-equivalent
duplicates (e.g. .cdf and .xls) for which the first will just get
thrown away. I didn't remove those though.
Finally, use of the module as a script as grown the -l and -e options
to toggle strictness and to do guess_extension(), respectively.
Doc and unittest updates too.