<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _update_compressed( collection_name, upsert, multi, spec, doc, check_keys, opts, ctx):
 """Internal compressed unacknowledged update message helper."""

    op_update, max_bson_size = _update(
        collection_name, upsert, multi, spec, doc, check_keys, opts)
    rid, msg = _compress(2001, op_update, ctx)
    return rid, msg, max_bson_size