code: def test_nulls(pickle_module):
      null = pa.scalar(None)
      assert null is pa.NA
      assert null.as_py() is None
      assert null != "something"
      assert (null == pa.scalar(None)) is True
      assert (null == 0) is False
      assert pa.NA == pa.NA
      assert pa.NA not in [5]
  
      arr = pa.array([None, None])
      for v in arr:
          assert v is pa.NA
          assert v.as_py() is None
  
      # test pickle roundtrip
      restored = pickle_module.loads(pickle_module.dumps(null))
      assert restored.equals(null)
  
      # test that scalars are weak-referenceable
      wr = weakref.ref(null)
      assert wr() is not None
      del null
      assert wr() is not None
  
imports: import datetime
  import decimal
  import pytest
  import sys
  import weakref
  import numpy
  import pyarrow
  import pyarrow.compute
  from pyarrow.tests import util
label_desc: Use image node_id 4 for calling a global function with example usage: test_nulls(pickle_module) without return types