<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def remove_expired_multipartobjects():
 """Remove expired multipart objects."""

    delta = current_app.config['FILES_REST_MULTIPART_EXPIRES']
    expired_dt = datetime.utcnow() - delta

    file_ids = []
    for mp in MultipartObject.query_expired(expired_dt):
        file_ids.append(str(mp.file_id))
        mp.delete()

    for fid in file_ids:
        remove_file_data.delay(fid)