code: def test_map0():
      assert None is func.map0(lambda x: x + 1, None)
      assert 3 == func.map0(lambda x: x + 1, 2)
      assert None is func.map0(len, None)
      assert 2 == func.map0(len, [1, 2])
  
file_path: catboost/library/python/func/ut/test_func.py
imports: import pytest
  import multiprocessing
  import random
  import threading
  import time
  import library.python.func
label_desc: Use image node_id 1 for calling a global function with example usage: test_map0() without return types