Function inversions_available 

pub fn inversions_available(
    cardinality: u8,
    forte_class: u8,
) -> Result<Vec<i8>, Error>

The inversions a set class comes in: [0] for one that is its own inversion, and [-1, 1] for the two halves of an inversionally related pair.

music21’s forteIndexToInversionsAvailable.

Errors

When the cardinality or the class number names no set class.