Function export_musicxml_partwise_report 

pub fn export_musicxml_partwise_report(
    score: &Score,
    identities: &[NotationIdentity],
) -> Result<NotationReport<String>, NotationError>

Exports canonical Score through the bounded MusicXML partwise profile.

Matching canonical paths in identities reproduce identifiers retained by a prior import. Missing identifiers are allocated deterministically.