code: def _update_compressed(
          collection_name, upsert, multi, spec, doc, check_keys, opts, ctx):
      
      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
docs: Internal compressed unacknowledged update message helper.