如何使用python拆分基于音高的midi文件？

import mido
import pretty_midi

midi_data = pretty_midi.PrettyMIDI('input.mid')

notes = midi_data.instruments[0].notes

note_groups = {}
for note in notes:
    pitch = note.pitch
    if pitch not in note_groups:
        note_groups[pitch] = []
    note_groups[pitch].append(note)

output_midi = pretty_midi.PrettyMIDI()
for pitch, note_group in note_groups.items():
    instrument = pretty_midi.Instrument(program=0)
    instrument.notes = note_group
    output_midi.instruments.append(instrument)

output_midi.write('output.mid')