Function cleaned_flat_notation 

pub fn cleaned_flat_notation(text: &str) -> String

A note name with each flat written b written - instead, as music21 spells it: music21’s cleanedFlatNotation. Only a b after a note letter is a flat.

use music21::common::misc::cleaned_flat_notation;

assert_eq!(cleaned_flat_notation("Cb"), "C-");
assert_eq!(cleaned_flat_notation("Ebb E bb"), "E-b E b-");