code: def echo(arg):
      return arg
  
file_path: distributed/distributed/protocol/tests/test_arrow.py
imports: from __future__ import annotations
  import pytest
  import distributed
  from distributed.protocol import deserialize, serialize, to_serialize
  from distributed.utils_test import gen_cluster
label_desc: Use image node_id 2 for calling a global function with example usage: echo(arg) and returns: arg