There is an unnecessary arguement inget_linestyle ofGraphicsContextBase. An unused arguement is required, which shouldn't be there.
It blocks any future 'propertification'...

I made the changes, but when trying to make a pull request against that commit, GitHub says there is nothing to compare?

Here is the commit:
https://github.com/JamesRamm/jplotlib/commit/0bab98249ee1b966eac96ac295e0e613a279b1cd