py7zr 3rd party project that use lzma module to compress/decompress 7-zip archive uses lzma._(encode|decode)_filter_properties.

These methods are public at first but become private in py3.4 at commit a425c3d5a264c556d31bdd88097c79246b533ea3

Here is a reason described in commit comment 
> These functions were originally added to support LZMA compression in the zipfile module, and are not of interest for the majority of users.

This is a request these methods to be public.

ref: py7zr: https://github.com/miurahr/py7zr