def update_note(note_id: NoteId, body: Body=None, done: Done=None) -> Note:
    """Update an existing note."""
    if note_id != 1:
        raise NotFoundError('Note does not exist')
    new_note = note.copy()
    if body is not None:
        new_note['body'] = body
    if done is not None:
        new_note['done'] = done
    return new_note
Update an existing note.