Function correct_suffix_for_chord_quality 

pub fn correct_suffix_for_chord_quality(
    chord: &Chord,
    inversion_string: &str,
) -> String

The inversion figure with the quality mark a chord’s fifth and seventh call for in front of it: music21’s correctSuffixForChordQuality. A diminished fifth writes o, an augmented one +, and a diminished fifth under a minor seventh ø; a figure that already carries the mark is left as it is.