music.is_playing() appears to require an argument

Hi,
It would appear that music.is_playing() requires an argument. The argument is not mentioned in the documentation and in the source it appears to be ignored. If the intention is to be able to ask whether a particular music file is currently playing (which would be nice seeing as though you can queue multiple files) then can I suggest the argument is optional and if not passed means ANY music file is playing.

Start by locating the music.is_playing() implementation and its documentation, then compare the documented signature with the source behavior. Resolve whether the argument should be optional or identify the intended semantics, update the documentation and relevant tests, and verify that the resulting API behavior is covered.

Written by the indexing model from the issue text.